Iām fascinated by your theory that Blaiseās bio dad was a Muggle - any other HCs about his family and what his mom was up to with 7 dead husbands?
I don't really have a headcanon per se, but I do have a theory on what I think may have inspired the creation of Mrs. Zabini and her seven husbands. So if you'll allow me to go completely off the deep-end for a moment and embrace the spirit that is this meme...
...then I think we can have some fun together, Nonny.
First and foremost: I don't think that JK Rowling ever intended to expand on Blaise's character.
This should be obvious to any book reader, considering that she quite frankly doesn't do that at all after mentioning his name at the end of Philosopher Stone's Sorting scene...
"Well done, Ron, excellent," said Percy Weasley pompously across Harry as 'Zabini, Blaise' was made a Slytherin.
- Philosopher's Stone, Chapter 7
...until he's reintroduced to us in Half-Blood Prince during the first meeting of the Slug Club.
He recognized a Slytherin from their year, a tall black boy with high cheekbones and long, slanting eyes; there were also you seventh-year boys Harry did not know, and squashed in the corner beside Slughorn and looking as though she was not entirely sure how she had got there, Ginny.
"Now, do you know everyone?" Slughorn asked Harry and Neville. "Blaise Zabini is in your year, of course--"
- Half-Blood Prince, Chapter 7
The reason why Blaise gets a description here is likely because, contrary to the text indicating that Harry recognizes him, Blaise has never actually appeared on the page before this moment and the reader would need to know the details of what he looked like in order to picture them in their heads. In fact, there was so little details released about Blaise prior to this moment that there was a large contingent of the fandom that believed that he was a girl prior to the release of Half-Blood Prince, as there hadn't even been a mention of Blaise's gender up until the scene I've quoted above. Ultimately, I don't think that it was ever JK Rowling's intent to actually get into Blaise's character but rather that she'd been aware enough of the fandom's interest in him that she eventually decided to include him in her latest novel after it became clear that a certain Slytherin character that she'd been trying for multiple books at this point to bring to the forefront just wasn't working out-- aka, Theodore Nott.
We also know that Rowling wanted to utilize Theo far more than she did for a fact, as she's talked about wanting to include a scene where he visited Draco at Malfoy Manor within Chamber of Secrets, and then trying again with Goblet of Fire when it didn't work out, before cutting the scene all together because it never seemed to work.
"I liked this scene [Malfoy + Nott] so much I tried to use it twice; unfortunately, it didn't work in either place so I finally laid it to rest in one of the cardboard boxes where I keep all my old drafts, notes, electricity bills and chewing gum wrappers."
- Extra Stuff, Malfoy & Nott
This is where we'd also have gotten a lot more background information on Theodore, where we'd learn that his elderly father was a former Death Eater like Lucius as well as how his mother had passed away while Theo was present in the room. We'd also get to see him interacting with Draco in a way that would force him to treat someone as an equal for the first time on-screen, and also allow the audience to gain the impression that Theo was significantly more clever than Draco was. It would present these two boys as being on similar paths to each other given their equally similar backstories, which is usually what feeds into my headcanon that Theo was actually Marked around the same time as Draco was because of their matching stories of Death Eater fathers that were named by Harry in his article with Rita that all eventually ended up in Azkaban after the utter clusterfuck that was the Battle of the Department of Mysteries.
But I think that it's also important to note that even without the deleted Malfoy & Nott scene, there was an attempt by Rowling to develop Theodore throughout Order of the Phoenix as he appears in multiple scenes throughout the book. Notably, we are first introduced to Theo in Care of Magical Creatures by presenting him amongst the unique few in the class that are capable of seeing thestrals.
Most of the rest of the class were wearing expressions as confused and nervously expectant as Ron's and were still gazing everywhere but at the horse standing feet from them. There were only two other people who seemed to be able to see them: a stringy Slytherin boy standing just behind Goyle was watching the horse eating with an expression of great distate on his face, and Neville, whose eyes were following the swishing process of the long black tail.
- Order of the Phoenix, Chapter 21
And then, we are officially introduced to Theo when Harry's interview comes out and we see him forgoing his supposed loner personality to sit amongst allies after his father is named as a Death Eater.
If anything more was needed to complete Harry's happiness, it was Malfoy, Crabbe, and Goyle's reactions. He saw them with their heads together later that afternoon in the library, together with a weeding-looking boy Hermione whispered was called Theodore Nott. They looked around at Harry as he browsed the shelves for the book he needed on Partial Vanishment, and Goyle cracked his knuckles threateningly and Malfoy whispered something undoubtedly malevolent to Crabbe. Harry knew perfectly well why they were acting like this: he had named all of their fathers as Death Eaters.
- Order of the Phoenix, Chapter 26
Theo's also notably present in Harry's NEWT Potion's class in Half-Blood Prince and is seen sitting beside Draco Malfoy.
Harry saw Malfoy lean close to Nott and whisper something; both of them sniggered, but Slughorn showed no dismay; on the contrary, he beamed and looked from Hermione to Harry, who was sitting next to her.
- Half-Blood Prince, Chapter 9
"Amortientia doesn't really create love, of course. It is impossible to manufacture or imitate love. No, this will simply cause a powerful infatuation or obsession. It is probably the most dangerous and powerful potion in this room-- oh yes," he said, nodding gravely at Malfoy and Not, both of whom were smirking skeptically.
- Half-Blood Prince, Chapter 9
We also get a lot of interaction with Theo's father as well, and that it goes beyond how he was supposed to be somewhat present in the deleted Malfoy & Nott scene.
However, in this scene Theodore's father (the same Nott who was badly injured in the closing chapters of 'Order of the Phoenix') goes to visit Lucius Malfoy to discuss Voldemort-related business and we see Draco and Theodore alone in the garden having a talk of their own.
- Extra Stuff, Malfoy & Nott
For example, we see him in the graveyard following Voldemort's resurrection within a book that I personally think would be the most ideal location for the deleted scene to have taken place, and see that he is trying to present himself to be one of the more faithful Death Eaters in Voldemort's presense.
"The same goes for you, Nott," said Voldemort quietly as he walked past a stooped figure in Mr. Goyle's shadow.
"My Lord, I prostrate myself before you, I am your most faithful--"
"That will do," said Voldemort.
- Goblet of Fire, Chapter 33
Theo's father also participates in the Department of Mysteries and that he's severely injured during the DA's initial counter attack.
Footsteps and shouts echoed from behind the door they had just sealed. Harry put his ear close to the door to listen and heard Lucius Malfoy roar: "Leave Nott, leave him, I say, the Dark Lord will not care for Nott's injuries as much as losing that prophecy-- Judgon, come back here, we need to organize!..."
- Order of the Phoenix, Chapter 35
And we even learn that his father was one of the early Death Eaters during Dumbledore's memory from when Tom came to the castle to apply for the DADA position.
"Then if I were to go to the Hog's Head tonight, I would not find a group of them - Nott, Rosier, Mulcilber, Dolohov - awaiting your return? Devoted friends indeed, to travel this far with you on a snowy night, merely to wish you lock as you attempted to secure a teaching position."
- Half-Blood Prince, Chapter 20
It is very clear that Rowling had an intent to develop Theodore as a character, regardless of why she might have been doing that (which my personal crack-pot theory boils down to him being the one to cast the Fiendfyre instead of Crabbe after his out-of-nowhere power-up in Deathly Hallows). And by comparison, Blaise didn't get much of any of anything outside of what little we do get in Half-Blood Prince and only really appears in one singular book to provide what was effectively much-anticipated fanservice and not much else. In fact, I wouldn't actually be surprised to find out if Blaise's involvement in the Slytherin Compartment Scene was originally supposed to be given to Theodore, as I think that it would have made a lot more sense to have Harry follow someone that the reader knew Malfoy had previously hung out with into the compartment and not a character that had last been seen six years prior during his Sorting.
But either way, what I think this all really adds up to is an indication that Rowling never actually planned on giving Blaise a larger role until both fan support of him and a lack of development for Theo pushed one character to the front and the other to the back of her narrative. And if that's truly the case, we now have to ask where the story of Blaise's mother come from, given that her son was never actually supposed to make it onto the page beyond his one tiny mention in Philosopher's Stone?
Well... I think that Mrs. Zabini and her seven husbands is a little Easter Egg that JK Rowling left herself regarding a very early draft version of Merope Gaunt.
[ Please note from here on out that I will be approaching Merope's story from as pure of a Doylist perspective as I possibly can. It is not the perspective that I normally take when I speak about Merope but for the sake of this analysis, it is something that I must do despite my overall dislike of the purely Doylist interpretation on what happened between her and Tom Riddle Sr. ]
It's important to understand that Rowling uses the various romantic subplots that exist throughout Half-Blood Prince to tell the story of Tom Sr. and Merope without actually showing the reader what JKR believes went down outside of the memories and scant guesses made about Voldemort's parents that we get to see. As a result, we can view Tonks' loss of her metamorphmagus powers due to Remus's rejection of her romantic feelings for him...
Harry thought she looked drawn, even ill, and there was something forced in her smile. Certainly her appearance was less colourful than usual without her customary shade of bubble-gum pink hair.
- Half-Blood Prince, Chapter 5
...as a parallel to how Merope's powers seem to wax and wain according to the presense of the men in her life and whether or not they accepted or rejected her.
āI think you are forgetting,ā said Dumbledore, āthat Merope was a witch. I do not believe that her magical powers appeared to their best advantage when she was being terrorized by her father. Once Marvolo and Morfin were safely in Azkaban, once she was alone and free for the first time in her life, then, I am sure, she was able to give full rein to her abilities and to plot her escape from the desperate life she had led for eighteen years.
- Half-Blood Prince, Chapter 10
"Ah," said Dumbledore, "perhaps she could. But it is my belief - I am guessing again, but I am sure I am right - that when her husband abandoned her, Merope stopped using magic. I don't think that she wanted to be a witch any longer. Of course, it is also possible that her unrequited love and the attendant despair sapper her of her powers; that can happen. In any case, as you are about to see, Merope refused to raise her wand even to save her own life."
- Half-Blood Prince, Chapter 13
We've also got Romilda Vane and her attempts to dose Harry with a love potion, and how it clearly mirrors how Dumbledore believes Merope initially dosed Tom Sr. with a love potion as well.
"Hi, Harry!" said Romilda Vane, the moment he had climbed through the portrait hole. "Fancy a gillywater?"
- Half-Blood Prince, Chapter 15
"I am included to think she [Merope] used a love potion. I am sure it would have seemed more romantic to her, and I do not think it would have been very difficult, some hot day, when Riddle was riding alone, to persuade him to take a drink of water."
- Half-Blood Prince, Chapter 10
We've also got Ron and his clear parallel to Tom Sr., as they are both victims of someone using a love potion on them. In fact, Slughorn even connects obsessive love to the use of love potions...
"Amortientia doesn't really create love, of course. It is impossible to manufacture or imitate love. No, this will simply cause a powerful infatuation or obsession. It is probably the most dangerous and powerful potion in this room-- oh yes," he said, nodding gravely at Malfoy and Not, both of whom were smirking skeptically. "When you have seen as much of life as I [Slughorn] have, you will not underestimate the power of obsessive love."
- Half-Blood Prince, Chapter 9
...and that the immediate infatuation and obsession that Ron suddenly felt for Romilda after being dosed...
"I can't stop thinking about her!" said Ron hoarsely.
Harry gaped at him. He had not expected this and was not sure he wanted to hear it. Friends they might be, but if Ron started calling Lavender āLav-Lavā, he would have to put his foot down.
āWhy does that stop you having breakfast?ā Harry asked, trying to inject a note of common sense into the proceedings.
āI donāt think she knows I exist,ā said Ron with a desperate gesture.
āShe definitely knows you exist,ā said Harry, bewildered. āShe keeps snogging you, doesnāt she?ā
Ron blinked.
āWho are you talking about?ā
āWho are you talking about?ā said Harry, with an increasing sense that all reason had dropped out of the conversation.
āRomilda Vane,ā said Ron softly, and his whole face seemed to illuminate as he said it, as though hit by a ray of purest sunlight.
- Half-Blood Prince, Chapter 18
...likely mirrored how Tom Sr.'s dosing resulted in him becoming increasingly infatuated and obsessed with Merope, which resulted in their runaway marriage.
"In any case, within a few months of the scene we have just witnessed, the village of Little Hangleton enjoyed a tremendous scandal. You can imagine the gossip it caused when the squireās son ran off with the trampās daughter, Merope."
- Half-Blood Prince, Chapter 10
As a result, it can also be assumed that Ron's horrified reaction to his love potion being lifted likely written to parallel Tom Sr's own when Merope stopped using her potion on him, thus showing what he went through without JKR actually having to write the scene.
Harry and Slughorn watched him. For a moment, Ron beamed at them. Then, very slowly, his grin sagged and vanished, to be replaced by an expression of utmost horror.
- Half-Blood Prince, Chapter 18
"Don't mention it, m'boy, don't mention it," said Slughorn, as Ron collapsed into a nearby armchair, looking devastated.
- Half-Blood Prince, Chapter 18
Romilda's story is also interesting in the sense that it allows her to fit into an archtype that Rowling frequently uses that I like to call the 'Supernatural Seductress,' which is basically a woman who use magical means to make a man become obsessively in love with them (often to their own detriment). Romilda is one of them, while Merope is another. But there is a third Supernatural Seductress that exists within Half-Blood Prince that I'd actually like to talk about now, if you don't mind.
Now, Fleur's 'True Love With Bill' plotline throughout HBP is a little odd to me, especially after reading through how she's shown throughout Goblet of Fire to be using her Veela abilities to ensnare men in order to date and eventually have sexual relations with them. Throughout Goblet, Fleur initially uses her abilities in an attempt to convince Cedric to come to the Yule Ball with her...
"She's part veela," said Harry. "You were right - her grandmother was one. It wasn't your fault. I bet you just walked past when she was turning on the old charm for Diggory and got a blast of it - but she was wasting her time. He's going with Cho Chang."
- Goblet of Fire, Chapter 22
...before she hits Roger Davies with enough of a blast of her allure that he's clearly out of his mind with an artificial infatuation towards her by the time they go on a date...
Fleur Delacour and Roger Davies stationed themselves nearest the doors; Davies looked so stunned by his good fortune in having Fleur for a partner that he could hardly take his eyes off of her.
- Goblet of Fire, Chapter 23
Roger Davies was watching her talk with a very dazed look on his face, and he kept missing his mouth with his fork. Harry had the impression that Davies was too busy staring at Fleur to take in a word she was saying.
- Goblet of Fire, Chapter 23
...and eventually having sex while Davies is still under the influence of Fleur's allure.
Harry looked around, back up the path, and saw Fleur Delacour and Roger Davies standing half-concealed in a rosebush nearby. He tapped Ron on the shoulder and jerked his head toward them, meaning that they could easily sneak off that way without being noticed (Fleur and Davies looked very busy to Harry), but Ron, eyes widening in horror at the sight of Fleur, shook his head vigorously, and pulled Harry deeper into the shadows behind the reindeer.
- Goblet of Fire, Chapter 23
Fleur and Rogar Davies had disappeared, probably into a more private clump of bushes.
- Goblet of Fire, Chapter 23
Also, we should note how Davies's reaction to Fleur is clearly mirrored in not only Ron and Harry's uncontrolled reactions to seeing Veela for the first time...
But a hundred veela were now gliding out onto the field, and Harry's question was answered for him. Veela were women. . . the most beautiful women Harry had ever seen. . . except that they weren't - they couldn't be - human. This puzzled Harry for a moment while he tried to guess what exactly they could be; what could make their skin shine moon-bright like that, or their white-gold hair fan out behind them without wind.. . but then the music started, and Harry stopped worrying about them not being human - in fact, he stopped worrying about anything at all.
The veela had started to dance, and Harry's mind had gone completely and blissfully blank. All that mattered in the world was that he kept watching the veela, because if they stopped dancing, terrible things would happen.
And as the veela danced faster and faster, wild, half-formed thoughts started chasing through Harry's dazed mind. He wanted to do something very impressive, right now. Jumping from the box into the stadium seemed a good idea. . . but would it be good enough?
"Harry, what are you doing?" said Hermione's voice from a long way off.
The music stopped. Harry blinked. He was standing up, and one of his legs was resting on the wall of the box. Next to him, Ron was frozen in an attitude that looked as though he were about to dive from a springboard.
Angry yells were filling the stadium. The crowd didn't want the veela to go. Harry was with them; he would, of course, be supporting Bulgaria, and he wondered vaguely why he had a large green shamrock pinned to his chest. Ron, meanwhile, was absentmindedly shredding the shamrocks on his hat.
- Goblet of Fire, Chapter 8
...as well as Ron's equally uncontrolled reactions to their part-human descendants after the fact...
It was the girl from Beauxbatons who had laughed during Dumbledore's speech. She had finally removed her muffler. A long sheet of silvery-blonde hair fell almost to her waist. She had large, deep blue eyes, and very white even teeth.
Ron went purple. He stared up at her, opened his mouth to reply, but nothing came out except a faint gurgling noise.
"Yeah, have it," said Harry, pushing the dish toward the girl.
"You 'ave finished wiz it?"
"Yeah," Ron said breathlessly. "Yeah, it was excellent."
The girl picked up the dish and carried it carefully off to the Ravenclaw table. Ron was still goggling at the girl as though he had never seen one before. Harry started to laugh. The sound seemed to jog Ron back to his senses.
"She's a veela!" he said hoarsely to Harry.
- Goblet of Fire, Chapter 16
...but how that same reaction can be parallel to Ron reactions after he's been dosed with love potion in parallel to Tom Sr...
"I can't stop thinking about her!" said Ron hoarsely.
- Half-Blood Prince, Chapter 18
"I love her," repeated Ron breathlessly. "Have you seen her hair, it's all black and shiny and silky... and her eyes? Her big dark eyes? And her--"
- Half-Blood Prince, Chapter 18
...because Ron is presented as unable to control himself around the allure of the Veela women, to the point where they start to appear drunk, similar to how Davies' apparently becomes non-functional Fleur's presense because of the aura she gives off. Either way, the affects of the love potion is clearly supposed to mirror the way that a Veela's allure works... and in turn that both of those things are supposed to parallel how a victim of the Imperius Curse feels when it's been placed upon them.
It was the most wonderful feeling. Harry felt a floating sensation as every thought and worry in his head was wiped gently away, leaving nothing but a vague, untraceable happiness. He stood there feeling immensely relaxed, only dimly aware of everyone watching him.
- Goblet of Fire, Chapter 15
And to further that parallel, we've once again got Ron getting caught up in a blast of Veela allure alongside noted Imperius Curse victim, Stan Shunpike.
Farther still along the path, they walked into a patch of silvery light, and when they looked through the trees, they saw three tall and beautiful veela standing in a clearing, surrounded by a gaggle of young wizards, all of whom were talking very loudly.
"I pull down about a hundred sacks of Galleons a year!" one of them shouted. "I'm a dragon killer for the Committee for the Disposal of Dangerous Creatures."
"No, you're not!" yelled his friend. "You're a dishwasher at the Leaky Cauldron... but I'm a vampire hunter, I've killed about ninety so far--"
A third young wizard, whose pimples were visible even by the dim, silvery light of the veela, now cut in, "I'm about to become the youngest ever Minister of Magic, I am."
Harry snorted with laughter. He recognized the pimply wizard: His name was Stan Shunpike, and he was in fact a conductor on the triple-decker Knight Bus. He turned to tell Ron this, but Ron's face had gone oddly slack, and the next second Ron was yelling, "Did I tell you I've invested a broomstick that'll reach Jupiter?"
- Goblet of Fire, Chapter 9
Harry suggests both a love potion and an Imperius Curse to be the methods through which Merope might have ensnared Tom Sr. in Half-Blood Prince, with Dumbledore being the one to provide correction with his belief that she more likely used the potion over an actual spell. But either way, the feeling that the victims of a love potion, Veela allure, and an Imperius Curse experience while being influenced by either of them has now been established as effectively the same, likely implying that they come from a similar source of magic. And that's why I think that we really need to take a look at yet another Supernatural Seductress that we get to see in action within Half-Blood Prince.
Tom Riddle has been implied throughout the series to be incredibly good at getting people to do what he wants them to do through his charming and seductive personality...
"If I say it myself, Harry, I've always been able to charm the people I needed."
- Chamber of Secrets, Chapter 17
...and it is in Half-Blood Prince that we first get an actual look at how he goes about doing that.
"I don't believe you," said Riddle. "She wants me looked at, doesn't she? Tell the truth!"
He spoke the last three words with a ringing force that was almost shocking. It was a command, and it sounded as though he had given it many times before. His eyes widened and he was glaring at Dumbledore, who made no response except to continue smiling pleasantly. After a few seconds Riddle stopped glaring, though he looked, if anything, warier still.
- Half-Blood Prince, Chapter 13
It is highly implied within this scene that the charm Diary!Tom was referring to might be an inherent ability to use a wandless, semi-verbal Imperius Curse variant, and that he's been able to do so since the age of eleven. This is likely what happened to Billy's Stubb's rabbit...
"Billy Stubb's rabbit... Well, Tom said he didn't do it and I don't see how he could have done, but even so, it didn't hang itself from the rafters, did it?"
- Half-Blood Prince, Chapter 13
"All sorts," breathed Riddle. A flush of excitement was rising up his neck into his hollow cheeks; he looked fevered. "I can make thinkgs move without touching them. I can make animals do what I want them to do, without training them. I can make bad things happen to people who annoy me. I can make them hurt if I want to."
- Half-Blood Prince, Chapter 13
...as well as to Amy Benson and Dennis Bishop, whom seem unable to physically speak of the events that occurred within the cave that Tom Riddle had brought them too.
"And then" --Mrs. Cole took another swig of gin, slopping a little over her chin this time-- "on the summer outing-- we take them out, you know, once a year, to the countryside or to the seaside-- well, Amy Benson and Dennis Bishop were never quite right afterwards, and all we ever got out of them was that they'd gone into a cave with Tom Riddle. he swore they'd just gone exploring, but something happened in there, I'm sure of it."
- Half-Blood Prince, Chapter 13
"I never did anything to little Amy Benson or Dennis Bishop, and you can ask them, they'll tell you!"
- Half-Blood Prince, Chapter 13
This ability is something that later appears to go hand-in-hand with Tom's ability to seduce people into doing what he wants, whether we're talking about Hebzibah Smith revealing Hufflepuff's Cup to him, the Grey Lady telling him where the Diadem was located, Ginny Weasley opening the Chamber of Secrets through the Diary Horcrux, or even Horace Slughorn telling him about Horcruxes in general (and if you've noted the Horcrux connection amongst those four examples, don't worry, we'll get back to that in a little bit). And if he is doing this through what is effectively a modified Imperius Curse that also runs in parallel to how love potions and Veela allure work, I also have to note how several things that we know are connected back to Salazar Slytherin also have elements of control attached to them as well. Parseltongue, for example, seems to come with the ability to control snakes and not just speak to them, as it's throughout the text that Tom's ability to control serpent is also tied back to his traced-back-to-Slytherin ability to speak the language.
"She [Nagini] underlines the Slytherin connection, which enhances Lord Voldemort's mystique; I think he is perhaps as fond of her as he can be of anything; he certainly likes to keep her close, and he seems to have an unusual amount of control over her, even for a Parselmouth."
- Half-Blood Prince, Chapter 23
There's also Slytherin's Locket, which seems to be able to influence the thoughts of those who wear it in a way that appears to be a muted form of how love potions, Veela allure, and the Imperius Curse work...
"Because that thing's bad for me!" said Ron, backing away from the locket on the rock. "I can't handle it! I'm not making excuses for what I was like, but if affects me worse than it affect you and Hermione, it made me think stuff-- stuff that I was thinking anyway, but it made everything worse. I can't explain it, and then I'd take it off and I'd get my head straight again, and then I'd have to put the effing thing back on-- I can't do it Harry!"
- Deathly Hallows, Chapter 19
...in regards to how Ron gets hit with the effects the worst out of all his companions. And before anyone says anything about that being the Horcrux's powers and not the Locket's itself, I'd like to point out that all three of the other objects owned by the Founders have magical powers associated with them...
"This [Hufflepuff's Cup] has been handed down in the family for years and years. Lovely, isn't it? And all sorts of powers it's supposed to possess too, but I haven't tested them thoroughly, I just keep it nice and safe in here..."
- Half-Blood Prince, Chapter 20
"The sword [of Godric Gryffindor] can destroy Horcruxes! Golbin-made blades imbibe only that which strengthens them-- Harry, that sword's impregnated with basilisk venom!"
- Deathly Hallows, Chapter 15
"It's [Ravenclaw's Diadem] a kind of crown," said Terry Boot. "Ravenclaw's was supposed to have magical properties, enhance the wisdom of the wearer."
- Deathly Hallows, Chapter 29
...so it goes to say that the Locket likely had powers too. And considering that most of the other defenses associated with the Horcruxes were curses attached to them by Voldemort himself (like the one on the Gaunt Ring or Tom's unusual weaponization of the soul piece within the diary) or don't have defenses at all (Harry, the Cup, the Diadem) but are instead protected by the environment that they've been placed within, I actually think that it's far more likely that the effects that Ron - aka, our Tom Riddle Sr. stand-in within Half-Blood Prince - feels when wearing the Locket are actually the abilities of the item itself rather than anything that has to do with the Horcrux. So again, we're looking at something that can be traced back to Slytherin that is also associated with control in a way that mimics the effects of the various methods that affect Ron-as-Tom Sr. in a way that were likely intended to mirror what Merope did to entrap Tom Sr. into becoming her husband... just like how Mrs. Zabini is implied to have done to her seven husbands too.
Zabini, who was interrogated after McLaggen, turned out to have a famously beautiful witch for a mother (from what Harry could make out, she had been married seven times, each of her husbands dying mysteriously and leaving her mounds of gold).
- Half-Blood Prince, Chapter 7
The number seven comes across the series multiple times, often in association with Tom Riddle in some type of way. Most obviously, we have his Horcruxes, but Tom is also defeated in Harry's seventh year and in the seventh book after all seven pieces of his soul have been destroyed. One of his more notable victims within the series is Ginny Weasley, who is the seventh child of Arthur, who's father (Septimus) is literally named 'the Seventh Son.' Also, Harry's noted ancestor, Hardwin Potter, was the eldest of the Potter Family's founding patriarch seven children and is the man that brought the Invisibility Cloak into the family through his marriage to Iolanthe Peverell, which is the familial connection that Harry has to the Gaunts and the Deathly Hallows (which is the reason for the naming of the seventh book and a very large chunk of it's plotline).
And then, of course, we've got how Hardwin Potter being the eldest of seven siblings is a clear contrast to Merope being the youngest of seven sister. And before you think that I've gone completely off the deep end with that last point because Merope canonically has one sibling (a brother named Morfin, whom we will talk about later too) I'd like to point out that I'm not talking about Merope Gaunt with that last statement.
I'm talking about Merope of the Pleiades.
The Pleiades are a series of seven sisters who were born to Atlas and Pleione within Greek mythology and are represented in the night sky within the Pleiades constellation. The dimmest star within that constellation is called Merope, after the seventh sister of the Pleiades who was said to have hid her face after having an affair with a mortal man. Obviously, this is likely the reason why JKR chose this name for the mother of Lord Voldemort, as Merope Gaunt's affair with Tom Sr. would have been seen as her turning her back on whatever 'divine' marriage that her family would have otherwise had her engage with to instead run away with an otherwise unworthy man, similar to that of her mythical counterpart. As a result, it's absolutely possible to count Merope Gaunt amongst the various ways that seven is brought up in the series, and how most of the examples of the number can be tied back to her and her son in some way, shape, or form. And that is especially true in regards to how how Tom uses his Slytherin-associated Supernatural Seductress charm to acquire knowledge concerning the creation of his seven Horcruxes just like how his mother might have not used a love potion in earlier drafts of her character but instead her own Slytherin-associated Supernatural Seductress charm to have her affair with Tom Riddle Sr. and produce their son... but specifically in a world where Merope Gaunt represented all seven of the Pleiades and went through six other 'divine' pureblooded husbands first before turning her back on divinity, dimming her star, and hiding her face to run off with final seventh mortal love.
If we are truly going to accept that the various romantic subplots of Half-Blood Prince are used to tell the story of Merope and Tom Sr. without actually showing the reader what happened, then we also need to accept that the various women (and singular man, in the form of Lord Voldemort) that we see engaging in the Supernatural Seductress archetype as versions of Merope throughout her story. At the same time, we also must believe that the love potion is actually a later-in-development metaphor for a Slytherin-associated power of seductive control that the Gaunt family might have possessed within earlier drafts, and that it worked in a way similar to the power we see within the Veela. So maybe in this early version, Merope would have initially appeared to us as being just as overwhelmingly attractive as her son (to the point where Tom is, mathematically speaking, the hottest character in the entire series), similar to that of the lethally attractive Mrs. Zabini.
Zabini, who was interrogated after McLaggen, turned out to have a famously beautiful witch for a mother (from what Harry could make out, she had been married seven times, each of her husbands dying mysteriously and leaving her mounds of gold).
- Half-Blood Prince, Chapter 7
In fact, I think that we actually know what that version of Merope might have looked like, as Romilda Vane's appearance is quite similar to that of a significantly more attractive version of Merope.
Her hair was lank and dull and she had a plain, pale, rather heavy face. Her eyes, like her brother's [which are described as dark], stared in opposite directions.
- Half-Blood Prince, Chapter 10
And one of them, a bold-looking girl with large dark eyes, a prominent chin, and long black hair pushed her way through the door.
- Half-Blood Prince, Chapter 7
However, this attractiveness would be brought upon by supernatural means and was not what she actually looked like, and that we're shown this through comparisons to how the Gaunt children look like all the colour has been sapped out of them...
The man [Morfin] before them had thick hair so matted with dirt it could have been any colour.
- Half-Blood Prince, Chapter 10
There was a scuffling noise in the corner beside the open window, and Harry realized that there was somebody else in the room, a girl whose ragged gray dress was the exact color of the dirty stone wall behind her.
- Half-Blood Prince, Chapter 10
...and how that compares to Tonks, who loses the ability to change her hair different colours and reverts to her 'natural' appearance after Remus rejects her...
Harry thought she [Tonks] looked drawn, even ill, and there was something forced in her smile. Certainly her appearance was less colourfol than usual without her customary shade of bubble-gum-pink hair.
- Half-Blood Prince, Chapter 5
And the meaning of Tonks' Patronus and her mouse-coloured hair, and the reason she had come running to find Dumbledore when she had heard a rumour someone had been attacked by Greyback, all suddenly become clear to Harry: it had not been Sirius that Tonks had fallen in love with after all.
- Half-Blood Prince, Chapter 29
...and we've already discussed how Tonks' loss of her powers was clearly intended to reflect Merope's loss of her own after Tom Sr. walked out of their marriage.
But at the same time, we can also connect that extreme beauty that I believe that Merope might have once had back to Fleur, who is also supernaturally beautiful and seems to ensnare various men in a similar way to how both Mrs. Zabini likely works concerning her seven dead husbands and how Merope currently works with her regarding her ability to steal Tom Sr. away from the girl he's currently interested in (like Romilda does with Ron regarding Lavender, or how Fleur planned on originally stealing Cedric away from Cho), simply because the beauty of a Veela is a false one. Like Tonks, Veela are shapeshifters. And when pushed to a state of extreme emotion like Tonks is, they will lose control of that beauty and reveal what they actually look like.
The leprechauns had risen into the air again, and this time, they formed a giant hand, which was making a very rude sign indeed at the veela across the field. At this, the veela lost control. Instead of dancing, they launched themselves across the field and began throwing what seemed to be handfuls of fire at the leprechauns. Watching through his Omnioculars, Harry saw that they didn't look remotely beautiful now. On the contrary, they're faces were elongating into sharp, cruel-beaked bird heads, and long, scaly wings were bursting from their shoulders--
"And that, boys," yelled Mr. Weasley over the tumult of the crowd below, "is why you should never go for looks alone!"
- Goblet of Fire, Chapter 8
In the case of Merope, her loss of her power might not have originally been a true inability to use magic anymore but rather the dropping of her supernaturally beautiful Romilda-style form to reveal the colourless and cross-eyed girl beneath. But part of me wonders if it actually went a bit further than that, that the original idea was for the Gaunts to actually be just as inhuman as the Veela are beneath their glamours and allure as a means of explaining why Merope's Supernatural Seductress of a son looks like that. Because if Merope Gaunt was originally supposed to go from being so supernaturally beautiful that she could have six pureblood men walk into her deadly marriage bed without a care in the world like a veela could, what if the loss of her powers mirror the loss of a veela's control over their own form too and revealed a monsterous, inhuman form beneath too. And that the rejection by her seventh husband is again mirrored in how Tom sheds his glamour of supernatural beauty to reveal his inhuman form too the closer he gets to murdering seven people to achieve his seven Horcruxes too?
The house-elf returned within minutes, followed by a tall young man Harry had no difficult whatsoever in recognizing as Voldemort. He was plainly dressed in a black suit; his hair was a little longer than it had been at school and his cheeks were hollowed, but all of this suited him; he looked more handsome than ever.
- Half-Blood Prince, Chapter 20
"I wonder whether you know what this is, Tom? Pick it up, have a good look!" whispered Hepzibah, and Voldemort stretched out a long-fingered hand and lifted the cup by one handle out of its snug silken wrappings. Harry thought he saw a red gleam in his eyes.
- Half-Blood Prince, Chapter 20
There was no mistaking it this time: Voldemort's eyes flashed scarlet at the words, and Harry saw his knuckles whiten on the locket's chain.
- Half-Blood Prince, Chapter 20
Harry let out a hastily stifled gasp. Voldemort had entered the room. His features were not those Harry had seen emerge from the great stone cauldron almost two years ago. They were not as snake-like, the eyes were not yet scarlet, the face not yet masklike, and yet he was no longer handsome Tom Riddle. It was as though his features had been burned and blurred; they were waxy and oddly distorted, and the whites of the eyes now had a permanently bloody look, though the pupil were not yet the slits that Harry knew they would become. He was wearing a long black cloak, and his face was as pale as the snow glistening on his shoulders.
- Half-Blood Prince, Chapter 20
Harry would have screamed, but he couldn't make a sound. Where there should have been a back to Quirrell's head, there was a face, the most terrible face Harry had ever seen. It was chalk white with glaring red eyes and slits for nostrils, like a snake.
- Philosopher's Stone, Chapter 17
Voldemort looked away from Harry and began examining his own body. His hands were like large, pale spiders; his long white fingers caressed his own chest, his arms, his face; the red eyes, whose pupils were slits, like cats, gleamed still more brightly through the darkness.
- Goblet of Fire, Chapter 33
What if the connections that those descended from Slytherin had to snakes was, in some sense, literal? What if, just like how the Veelas' true forms are bird-like, the true visage beneath the inhuman beauty of the Slytherins was actually that of a serpent-man and that the version of Voldemort that Harry goes up against throughout the series was just him being unable to maintain that Veela-style glamour and showing what he and his family actually looked like after his use of Dark Magic stripped away the mask and pretense of humanity? And again, before you think that I've gone completely off the deep end, I think that there's a potential avenue to explore this due to yet another connection back to Merope... or rather, that of her brother.
Because do you know where Morfin's name actually comes from?
It comes from the name Morfryn, which is the name of the Merlin's father within certain Welsh texts. Merlin's traditional backstory has him being given his supernatural powers (of which include the ability to shapeshift) through the union of his mortal mother and demonic Incubus father, and that he was saved from his original prophesized fate of becoming the Antichrist because of the intervention of a teacher. Because when you think about it, there's a lot of imagery within the text that presents Voldemort as a Dark version of Dumbledore, whom himself is very clearly modeled after the modern depiction of Merlin with his long beard and equally long robes. So if Dumbledore is the version of Merlin that turned out good and eventually became the teacher of the King-Arthur-as-Godric-Gryffindor stand-in that is Harry, then Voldemort represents the version of Merlin that rejected that teacher's intervention and became the Antichrist a la how he 'rejects' Dumbledore's hand (and that of his King Arthur student's attempt at getting him to experience remorse) and therefore all of his attempts to save him from his predestined fate. As a result, presenting Merope as Voldemort's shapeshifting seductress parent and Tom Sr. as her mortal/unmagical parent would allow for an interesting gender-flipping of Merlin's origin story, and potentially even pseudo-conform the Gaunt sibling incest if we're willing to assume that Morfin was the original seventh husband that Merope was supposed to marry before she dimmed her starlight and lost her shapeshifting abilities because she ran off with a muggle/mortal man. And before you go, "Okay, the mythology fits and it's definitely possible that JKR is telling the story of Merope Gaunt through the romantic subplots within Half-Blood Prince, but I do think that you're reaching a step too far by assuming that Mrs. Zabini and her seven dead husbands are an Easter Egg to an early development version of Voldemort's origins," I have one question to ask you.
Do you know the name of Merlin's teacher that saves him from his fate of becoming the Antichrist?
So yeah, I don't think that there's anything that's actually going on in-universe with Mrs. Zabini and her seven husbands. Instead, I think that Rowling not only used the various romantic subplots of Half-Blood Prince to tell the Doylist-canon story of Merope Gaunt but also utilized a convenient opportunity created by Blaise's popularity amongst fans to tell the cut original draft version of Merope as well, and that Merope might have originally been intended to be a shapeshifter with seductress powers similar to that of a Veela that her own son eventually inherited alongside her Parseltongue, that she also represented all seven of the Pleiades through seven marriages to seven equally dead husbands that are then mirrored within Voldemort's seven murders that were used to create his seven Horcruxes, and that it was got cut sometime between when she was writing Goblet of Fire and the publication of Half-Blood Prince.
Other topics of note that I wanted to discuss but couldn't find the space/energy in which to do so, so they're getting dumped here in a bullet point list:
Ron's clear weakness to Veela allure is usually a sign that it's being used, which does imply that Fleur might be using it throughout HBP given how he's clearly being affected by it. This is why I think that Fleur might not have originally been intended to be Bill's love interest (and that I think it might have originally been Tonks), but that Fleur's hold on Bill was supposed to be compared to Merope's hold over Tom Sr. and that Ron getting affected by the allure wasn't originally supposed to represent his immaturity but is rather a hold-over from a previous plot where it was a sign that Fleur's allure was going off.
Ron's fear of being around Fleur also clearly mirrors his horror to having Romilda's love potion lifted, as well as his clear discomfort of Romilda being mentioned afterwards.
The further Tonks-Merope connection that is the Pleiades are a set of seven nymph sisters.
In fact, if we consider Voldemort as Merlin-the-Antichrist and Dumbledore as Merlin-the-Saved, and we consider my crack theory of Tonks being Bill's original love interest, we can now have the opportunity to parallel Fleur and Tonks as versions of Shapeshifter!Merope who's love for their husband was forced via supernatural means and truly unrequited one who's love could have potentially been pure and untainted.
Merope of the Pleiades' mortal husband was Sisyphus, who's attempts to cheat death got him cursed by the gods to suffer in eternal punishment within the afterlife, where he is forced to push a massive boulder up a hill only for it to inevitably roll back down whenever he gets near the top. This is clearly paralleled in Voldemort's own posthumous fate, where his destruction of his own soul has damned him to remain in limbo forever, unable to move on.
If we consider the idea that Merope was written to be the Anti-Lily, one could also make the assumption that the seven dead husbands were part of a spell that might have been intended to create the actual Merlin-as-the-Antichrist, and that Merope's decision to abandon her chosen husband, Morfin, might have originally been her attempting to avoid the fate of becoming . If so, then in parallel to the fate of Sisyphus, Merope still ended up creating the Merlin-as-the-Antichrist figure through her own actions, as Rowling has stated that it was the unloving union between her and Tom Sr. that took away Voldemort's ability to love and turned him into the monster he became later in life and that her laborious attempts to escape the inevitable where ultimately futile and thus, Sisyphean.
While Blaise's mother is definitely an exact fit to the Supernatural Seductress archetype, Blaise himself is a still a seductive character, as Pansy is clearly trying to impress him throughout the Slytherin Compartment scene despite the fact that she's likely with (or, at least, wants to be with) Draco at the time-- aka, a gender-flipped, non-magical version of what happens between Merope, Tom Sr., and Cecelia.
If we're to take my little crack theory about Theodore being the originally intended fifth occupant within the Slytherin Compartment scene instead of Blaise as fact, Pansy's potential interest in Theodore when Draco's back is turned can be seen as a parallel to Ron's belief that Hermione is looking at Harry when his back is turned, which is what the Locket uses to fuel his fear and divide the Trio in the tent a book later.
All on-page examples of sex within the Harry Potter series can be paralleled directly back to Merope Gaunt.
The things that Ron experiences while wearing the Locket being an ability of the Locket itself and not the Horcrux is why I generally headcanon that Merope used the it and not a love potion to control Tom Sr., if only because I think that Marvolo and Morfin were using it to control her within their household as well and that her decision to stop hurting Tom Sr. was also an acceptance that the sexual violence she experienced herself under her father and brother was wrong as well.