Hi! Here is an interesting ask.
What if Blinky and Aaarrrgghh found and raised an amnesiac human Jim since he was five?
This version of Jim found out he could manipulate and control plants a few weeks after Blinky found him due to a fight with Draal, but due to the amnesia, he can't recall who he got the ability from.
So, in this AU, Jim meets Nari really early (even before his father left) and befriends her. Nari doesn't mind as she is kind to children. Alas, this friendship leads to a horrible accident and Jim is mortally injured. To save him, Nari pours a lot of her magic into his body, so Jim survives but loses his memories (and his plant control is another side effect).
Blinky and Aaarrrgghh find the confused child in the forest and as Jim only can tell his name, they take him with them to the Trollmarket. Initially, it was a temporary measure as they hoped that going through Arcadia might help Jim to remember where his house is but it simply doesn't work and Jim stays at the Trollmarket.
Draal doesn't start a fight with Jim (from his point of view that one is just a weak fleshbag welp) - Jim is the one who initiates it because Draal is rude to Blinky whom Jim already likes a lot. Draal just intends to scare Jim, but the fear leads to unlocking Jim's plant-control abilities. After learning about those, trolls at the Trollmarket start to think that Jim is connected to the supernatural, so looking for his home in Arcadia is rather pointless.
Jim grows around trolls and it shows as he has no proper idea how human society works as his main source is Blinky and his knowledge is often 'off'. Initially, both Blinky and Aaarrrgghh try their best to cook something Jim can eat, but their attempts are so bad that Jim starts to learn to cook himself. His recipes are unorthodox but he is surprisingly good at that.
In this AU Jim is fluent in troll language and has read a lot of books from Blinky's library. He still wants an adventure, but more to prove himself (even if trolls at the Trollmarket adore him, they still consider him weak).
As for Barbara, her marriage with James ended with even more heartbreak as she realized that he not only cheated but also didn't care about Jim to keep searching for him. Barbara refuses to think that her son is dead and secretly keeps searching through all of the years.
Toby had no opportunity to befriend Jim, so he's friends with Eli and they often go searching for creeps together. Ironically, Toby doesn't believe in magical creatures or aliens, and after each of their common night missions, he is even more sure that everything is just Eli's imagination.
Barbara is the one who finds the amulet in this AU, but as Eli and Toby visit her the night when Blinky, Aaarrrgghh, and Jim barge in, they are also involved.
Barbara suspects that Jim can be her son (and her suspicions grow only stronger after she learns his backstory), but she is scared to talk to Jim about it as she expects him to push her away (as she hasn't been a part of his life all these years).
Meanwhile, Strickler has absolutely no idea who the new Trollhunter is (he doesn't even think that it can be not a troll). Bular decides to wreck some chaos and lure out the champion. Toby and Eli are attacked, but Barbara comes to their help and Jim arrives just in time to slow down Bular with his magic.
Anyway, now both Bular and Strickler know that the Trollhunter is a human woman, and Strickler decides to identify her and use a seduction approach (and as we all know, he falls in love himself).
As for Toby and Eli, they decide to teach Jim more about human stuff and start to take him out to explore. Jim manages to get into a fight with Steve (and absolutely obliterate him before the crowd) and falls in love with Claire after bumping into her accidentally. Claire is curious about who is the new guy, and Eli lies that Jim is his cousin. Later, during their second meeting, Jim forgets about this version and insists that he's Toby's cousin. This inconsistency makes Claire suspicious, and she starts her own investigation, which leads to her discovering Jim's secret too.
The Janus Order starts to doubt Strickler's loyalty, so they decide to send an additional spy. That is how NotEnrique gets into Claire's family. He gets more than enough information as no one suspects him at first. Still, he gets careless eventually, and Claire learns that her brother is an impostor.
As for Strickler, he actually starts to play his own game earlier as he wants to keep Barbara safe. At some point, he realizes that letting Gunmar out isn't in his interests and tries to recruit some allies within the Janus Order. It doesn't work though, as everyone suspects some ulterior motives. Nomura is the only one who agrees to cooperate and Strickler is forced to unseal Angor Rot as he needs to obliterate Bular.
Strickler commands Angor to join the Trollhunter's team and help Barbara slay Bular. Angor isn't trusted at the Trollmarket though, as everyone remembers that he was Morgana's champion. However, Barbara and Jim decide to give him a chance.
Jim keeps learning more about human life and Barbara makes a hopeful suggestion that he can try to live among humans and go to school with his friends. She proposes that he stay at her house (hoping that he will agree), but Jim is still reluctant. Sure thing, he has bonded with Barbara, considers her close to family level already, and enjoys communicating with Toby, Eli, and Claire, but human society remains too foreign to him.
Meanwhile, Claire who is upset and angry for not noticing that her brother was switched with the changelings, starts to take staff fighting lessons from Angor. Angor also senses her magic talent and proposes to her to learn that one too (he isn't trusting of wizards, but he feels that Claire might develop her magic to the level when she can break his binding to Morgana). He doesn't reveal everything to her though.
Nomura ends up compromising her secret identity and the bridge location, but Strickler is smart enough to keep his own secret hidden while developing his relationship with Barbara.
The team Trollhunters defeats Bular and secures the bridge. Nomura doesn't get trapped as she isn't present during the final battle per Strickler's suggestion.
Strickler thinks that everyone is great now and plans to reform the Janus Order into an organization to capture the world for themselves. His only issue is that all the familiars are in the Darklands, meaning that Gunmar has control over changelings' ability to transform. So Strickler decides to fool Gunmar and stall for as long as possible. He genuinely believes that the Trollhunter's side has no interest in opening Killahead.
However, Strickler doesn't consider that Barbara plans to travel to the Darklands and get back Enrique (as well as other kids). She doesn't want to risk her young allies though, so she doesn't plan to take any teen with her, which heavily upsets both Jim, who considers himself a competent fighter, and Claire, who believes that saving her brother is her mission, rather than someone else's.
Meanwhile, Angor Rot who has more respect at the Trollmarket now for helping to defeat Bular, decides to reveal Strickler's true identity to Barbara and request her help in getting free. Barbara is both sad and furious to learn Strickler's secret as she has genuine feelings for him and believes that everything from his side is just a lie. She doesn't give Strickler any chance to explain himself.
And it's not the only trouble Strickler faces as there is a rebellion within the Janus Order, and both Strickler and Nomura are forced to run from everyone.
They both decide to bargain with Barbara's team, proposing Angor's freedom and the Eye of Gunmar in exchange for protection. Barbara is still angry, but she agrees.
Strickler realizes what exactly he lost and decides to venture to the Darkland alone and save familiars to show Barbara that he is interested in changing. He tricks Barbara into test-opening the bridge and sneaks to the Darklands in secret. He doesn't realize that Jim and Claire both have the same idea and sneak there too.
All three meet accidentally in the Darklands and form the team. As Strickler knows the layout of the Darklands, they don't have much trouble finding the nursery, but it's when they face a huge problem as goblins and Gumm-Gumm soldiers discover them. Claire escapes with Enrique, while Strickler and Jim stay back to stall for some time and then escape. They miscalculate though, as Jim's ability doesn't work in the Darklands, so both are captured.
Meanwhile, at the Trollmarket, the Tribunal finds out that the gates to the Darklands are open when Claire gets back. The bridge is destroyed per Usurna's command and despite Barbara's, Vendel's, and Blinky's protests, the plan is to dump fragments somewhere. The Tribunal is even more willing to execute the plan than in the canon as their Trollhunter isn't in the Darklands and Jim is considered an adequate sacrifice (and well, the Tribunal isn't interested in saving Strickler).
Barbara's team recovers the Bridge similar to how it happened in the canon. Steve accidentally stumbles upon them and learns the truth as well.
As Barbara has the amulet, the team has no trouble going to the Darklands. Steve is the one they leave watching the gate (as no one thinks that something bad can happen). In the Darkland, they save all the familiars and free prisoners from Gunmar's prison. They don't realize that Gunmar uses the distraction and goes out with a full squad of Gumm-Gumms (Steve sees them and runs away before anything happens).
Barbara's team isn't welcome at the Trollmarket after their stunt, besides Usurna gets in contact with Gunmar way earlier, resulting in a full takeover.
Strickler goes around, trying to recruit some of his fellow changelings, who currently have lost their ability to change forms, but only a few follow him as they, apparently, have a new leader. The leader in question is Morgana herself, who is searching for a good vessel to possess (and she is pissed that Angor is out of her control). Nevertheless, her involvement protects changelings from outright extermination by Gunmar's hand.
The Janus Order kidnaps Claire whom they deem to be the appropriate vessel and finding her turns out to be a problematic quest as only Angor Rot is skilled in shadow arts and Morgana blocks him.
The situation hurts Jim the most (as Claire is his girlfriend by this point). He is upset and subconsciously taps upon an ability he hasn't known to have which is sensing human souls. Jim temporarily senses all the souls in the world (and nearly goes crazy), but these mere moments are enough to locate Claire. The team raids the Janus Order's hideout and frees her. However, during the capture changelings used all kinds of methods to break Claire's mind, so Morgana still has some hold on her psyche (not to the point of full takeover still, but she can seize control for some time).
The only way to fight it is to find a skillful wizard. Blinky suggests finding Merlin's staff as he was the creator of the amulet. Getting rid of Morgana is vital at the moment as it stops Morgana from joining forces with Gunmar. Morgana would gladly try to possess someone else, but Claire basically traps her within her own soul, even if it's dangerous.
What neither Claire nor the team Trollhunters realize is that Morgana wants to get Merlin's staff, so visiting her tomb is vital for her too. She sends Claire some visions about its location, which everyone thinks to be a side effect of shadow magic.
Claire, Jim, Toby, Draal, and Angor Rot decide to go searching for Merlin's tomb while everyone else stays behind to stall Gunmar's army. Before Jim heads out, Barbara has a talk with him (as she is scared that there might be no other opportunity after, with all the big fighting incoming), telling him that she is nearly 100% sure he is her long-lost son, but even if he isn't, she still considers him her son.
Jim and his part of the team discover something odd during their quest - it's as if someone is pursuing them. But only at Merlin's tomb, when they locate the staff, the pursuer reveals himself. He introduces himself as Green Knight and demands to give him the staff. The fight for it is short as unlike everyone else, Green Knight can use his abilities inside the tomb. Draal is injured, and Angor gets hit by the cursed shard, falling under the Green Knight's control. Green Knight withdraws with the staff and Angor as the tomb starts to collapse. Jim, Claire, and Toby try to escape with injured Draal and stumble upon the sleeping Merlin.
Merlin is surprised to see all of them as he has expected the Trollhunter to wake him up, but still, he goes with them back to Arcadia. He is also quite at a loss about Green Knight and his identity, so he decides not to delay contacting Douxie.
Meanwhile, Morgana is also rather confused and pissed because of the Green Knight's appearance to the point that she comes to Claire in her dreams and proposes cooperation. Claire doesn't believe her though, thinking it's just a scheme to trick her.
Merlin examines Claire and admits that he cannot do anything with her situation as he isn't skilled in the dark arts, which only angers everyone.
The team tries to deduce who is the Green Knight and why he took Merlin's stuff, but have no success as he apparently doesn't contact Morgana's or Gunmar's party.
During one of his strolls, Jim meets Nari. She seems extremely familiar to him, but he cannot remember much. Nari apologizes to him for changing his life so much, and Jim finally gets his blocked memories back. Nari also tells him that she unwittingly turned Jim into her champion when she poured her magic into him and that the Arcane Order will try to make their move. She guesses that Green Knight is somehow connected to them and that he took the stuff to prevent the Trollhunter's party from defeating Gunmar.
Gunmar decides to attack without starting the Eternal Night - he's rather disappointed in Morgana by this point as her independent actions only complicate everything. He is thinking about capturing Merlin instead and forcing him to find another solution for trolls.
As for Barbara, she and her allies were gathering all possible allies to fight against Gunmar.
The final clash happens in the forest at night, and the Trollhunters' team wins. Most of the damage is prevented too, and the Heartstone, despite being drained is mostly intact, so no one goes to New Jersey, instead searching for a way to revitalize the Heartstone.
Morgana (through Claire) tries to bargain with the different team members to get her freedom, but everyone is cautious, besides, Merlin makes it clear that without his staff there is no way to free Morgana's body.
Bellroc appears before Claire, proposing giving Merlin's staff in exchange for telling them the location of Genesis Seals. Despite not knowing what those are, Claire feels that something is off and refuses. Morgana hears the proposal too, and starts to wonder what the Arcane Order plans as she also knows about the seals and what they can do. Morgana is against world destruction, she simply wants to reform it.
Meanwhile, Jim is cornered and attacked by Skrael, who is searching for Nari and mistook Jim's energy for hers. Jim ends up captured and the Arcane Order realizes that he can also wake Nari's titan and is definitely easier to mind-control.
The team learns about Jim's capture, and everyone, except Merlin, wants to save him. Merlin, however, shows some anxiety when it comes to his staff, revealing begrudgingly that he hid Genesis Seal within it and that the Arcane Order unknowingly possesses the key to world destruction already. However, his plan is to pretend that Genesis Seals are still in his possession and stall for as long as possible.
Morgana makes a deal with Claire, promising her to save Jim if she temporarily gives her full control over her body. Claire agrees after some consideration, fully realizing that Morgana's shadow magic is superior.
Morgana (in Claire's body) locates the Arcane Order's base, finds Angor, liberates him from the Green Knight's control, and teleports him away without explaining a thing. Then she comes over to Bellroc and Skrael (as Jim is near them too) and proposes to get them Genesis Seals in exchange for the staff which can free her from her confinement. Claire hears that from the confines of her mind and is enraged, thinking that Morgana has deceived her. However, it turns out that Morgana tricks the Order as she teleports the staff inside the Shadow Realm the second it's in her hand. Enraged Bellroc casts the spell which binds Morgana to her sealed body, but Claire manages to escape together with Jim.
However, during Morgana's stunt, Merlin and Douxie are attacked by the Green Knight while they are meeting with Nari. Merlin discovers that the Green Knight is King Arthur and gets mortally injured while protecting Douxie. Nari is captured.
Back at the Trollmarket Jim decides to use Merlin's staff and free Morgana as his token of gratitude (as he is a human who can speak Troll language, it's possible for him). Morgana is surprised to be free and calls Jim naive for her decision as she might try to take over the world in the future. However, she has already given up on that plan after seeing that humans and trolls can work side-by-side and the world may have a better future.
Her plan is to use the same spell as Merlin and seal Bellroc and Skrael. Douxie returns with the staff, updating everyone about the recent developments. The team decides to use Genesis seals as a lure, and Douxie recovers them with the help of Charlemagne.
Morgana is preparing the trap for her sealing technique with the assistance of Douxie and Claire. Everyone else faces the Green Knight, with Angor Rot finishing him but dying in the process.
Morgana's plan works, and she seals Bellroc and Skrael (Nari comes to help her too). She puts more into it to make it more effective, so she crumbles to dust in the process, but the world is saved.
