After days of working on it, I finally finished a hollow knight theory that may help answer one of the biggest unsolved hollow knight mysteries so far.
Today, I offer you :
Esmy and the mystery of the nailsmiths
A couple days ago, I randomly started thinking about the broken vessel. I always found it strange to see that they used what seems to be nail arts, and I recall more than once seeing people making headcanons about them possibly being raised by the nailmasters.
But after a couple hours of thinking ... I'm starting to think that not only this is the truth, but it could help solve the long lasting mystery of what broke apart the nailmasters, and who is Esmy
To start it off, I'm gonna list off the things that I think are noteworthy about the broken vessel and that could be used further down in the theory.
First of all, the nail arts. While they may not be the exact same as the ones we've seen, I'd say it's pretty easy to see that they are able to use what seems to be a dash slash, and the attack where they wave their pin around their head is one we can see sly use in the pantheons.
Then, one of the most obvious things that differentiate them with other vessels is the fact that they grew. Not a single vessel grew outside of the Hollow knight, not even the protagonist. And the pure vessel's hunter journal entry states that they were "trained to prime form", meaning that the thing that makes vessel grow may literally be the act of training. And if the broken vessel was trained as a nailmaster, it would make sense that they grew.
The broken vessel can be dreamnailed, meaning they're not empty. And it seems the game leads us to believe that what removes the emptiness of vessels is growing affection towards others, with the knight slowly starting to appreciate Hornet and Quirrel and therefore losing their hollowness.
Now, let's move on to the little we know about Esmy.
Esmy is mentioned once by Sly while he's under the Radiance's influence at the beginning of the game. They are mentioned nowhere else in the game, Team Cherry said in an Reddit AMA that they are "someone who still lingers in Sly's dreams", and when dreamnailed, sly mentions that he hopes all three of the nailmasters are doing good, but nothing about Esmy.
Furthermore, when giving you the nailmaster's charm, he talks about his "remaining pupils". He's not a teacher anymore, so that can't be interpreted as the ones that are still his pupils to this day.
With all of this information and the knowledge that dreams are associated with the dead, I think it's safe to assume that Esmy was Sly's student who died at some point. And with the idea of Esmy dying before any of the nailmasters or even sly ... I don't think this death came from old age.
And the last part before we start making links between all of that : the Nailmaster's broken relationship.
It seems that all nailmasters used to have a close relationship, and it's quite obvious something pretty heavy happened between all of them. Something big enough that it made Mato resent Oro, made Oro isolate himself and stop giving news to his brothers who don't even know he's alive, and made Sheo fully drop his nail and start being a peaceful artist.
We don't know what happened exactly and the knowledge we have of everything is very vague. But it seems that Sheo doesn't fully know what happened, and mainly, Oro owes something to Mato and Mato refuses to let go of it.
Thing is, it's a bit hard to imagine what would Mato want from Oro. Money ? Wouldn't make sense. Oro's the one who asks for money from the knight. Mato doesn't think about money it at all, he's just extremely excited to get a pupil. He seems everything but greedy. An item ? Feels strange. Oro doesn't strike me as a thief, but there's also no item that is ever mentioned by the nailmasters that could fit this idea of being so important it broke a relationship. A duel then maybe ? That's too easy. If Mato just wanted to fight him, learning his location should be enough for him to track him down and ask for a battle, and it wouldn't make sense as to why Oro is delaying it so much.
No. I think what Oro owes to Mato is an apology.
Now, let's finally dive into linking all of these informations and imagining what could've happened.
The broken vessel was seemingly trained by someone due to their ability to use nail art and the fact that they grew. Sly had a student that is seemingly dead, and something destroyed the relationship between all of his students, the Nailmasters. I think the broken vessel is Esmy, and their death affected everyone in a different way.
The only time Sly ever mentions Esmy is very peculiar in my opinion. "Esmy... How much deeper do we have to go ?"
To me, if this character is important and mentioned only once, it would make sense that the sentence around them would have significant lore implications, and talking about going deeper isn't something chosen randomly. And where do we find the broken vessel ? In the abyss. In fact, we find them pretty close to their birthplace, which I think would make sense as a destination if they were trying to lead people somewhere. If Esmy didn't have a voice yet still wanted to explain their origins to their close ones, the only way they could do so is to show them.
How did they die then ? There are a couple possible explanations. But if we want to make a link between all of this, I think it's safe to assume it has something to do with Mato and Oro's fight. And since Mato is blaming Oro for something, I'd say it's either that :
Esmy was endangered in some way, and Oro didn't help them. Either because he physically couldn't (was already in a battle against something else) or because he was too scared.
What I think is more likely : Esmy got possessed by the radiance and Oro killed them, either to put an end to their suffering or to defend Mato.
There are several reasons why I think the second option is more likely. Oro doesn't look like someone who'd get scared. Mato would probably understand if it was just an accident. The broken vessel is already well known to be possessed by the radiance in-game. And we know that the radiance would have an easy access to their mind since their last action after the knight defeats them is try to reach out to them. Meaning that they care, they feel affection, and therefore have a mind the radiance can manipulate.
Mato is someone definitely more happy, optimistic and very social compared to Oro who seems more pessimistic and views things in a darker light. I feel like them having a conflict over whether or not they could've saved Esmy could make a lot of sense, with Oro defending his actions saying that killing them was the right thing to do to defend themselves/cut their suffering, and Mato probably believing there could've been a way for them to be saved.
It's also important to notice the behavior they have towards the knight. Mato is immediately very protective and affectionate, excited to be a teacher and immediately calling himself the Knight's father. He's very open about his feelings and tries to be very cheerful, only breaking character when he notices Oro taught the knight which makes him immediately mention he still owes him something.
Oro, on the other hand, tries everything he can to distance himself against the knight. He makes them pay a high amount of money to get his nail art. He tells them to get out of his house immediately after teaching them. But he cares deeply, and it's ultimately shown by the delicate flower. When you gift it to him, he tells the knight to get it back or else he'll throw it in the trash. But when you return, you find out he carefully put it in a vase.
He tells the knight Mato will have to be waiting for what he's owed a long time. If it's an apology, it could either be because he thinks he did nothing wrong, or because apologizing about literally killing a close one is extremely hard and he himself has to grieve properly first. When you dreamnail him, Oro talks about how Mato quite literally saw him as an enemy during some time, and how he wishes to tell him why he took this path. He may have never gotten an occasion to fully explain what happened because things immediately got heated between the two. Mato may not even know that he was also hurt in this situation.
Sheo had always talked about finding a new path away from the blade according to Mato. But I think something must've pushed him to actually do it, just like something must've pushed Sly to become a shopkeeper and step away from his original path.
Sheo does mention that Oro seems haunted by something, and wonders if it's fear, guilt or shame that drove him away. I think everything could fit this situation, even if Sheo doesn't seem to know the full story. Oro fears the retaliation and hate from the brothers he loved. He feels guilty for his actions. And more than anything, he's ashamed that he both couldn't save Esmy, but also couldn't face the consequences of his actions.
TLDR :
The broken vessel seems to be Esmy, a mysterious character mentioned by sly. Them training as a nailmaster would explain why they grew taller and why they knew nail art
Their death could be the origin of the nailmasters falldown. Mato is pissed at Oro because he killed them after they were infected, and Esmy's death affected Sheo and Sly enough that they stopped being nailmasters.
