cw for mentions of stabbing and wounds and mind control, and lots of pain via ultima transformation.
emerald secret au in which the romance plot is removed, and ein's obsession with aphmau hinges on him wanting to make her his 'real' sister, i.e a werewolf. he enlists michi's help and captures lucinda first, same as in canon, and uses a potion michi made to temporarily put her under his control, just long enough for her to decipher the potion book he has and start making the forever potions.
he uses lucinda to lure aphmau and aaron out just like in canon, then seperates them in the woods via michi hijinks, then captures aphmau.
he uses the first forever potion on her, brainwashing her into thinking they've been siblings all along and that she loves him (like a brother I must stress that this is familial love), and will do anything he says. the second forever potion is to make her despise aaron, though he doesn't use it yet since it's not complete: it needs something of aaron's, such as a lock of hair, for it to work as intended. he also puts lucinda under the influence of a forever potion, just in time for the first one to run out, so she'll keep serving him.
he uses aphmau to lure someone else in (doesn't matter who, he just needs another minion), and she ends up bringing zane, who is also put under a forever potion like normal. only now does ein go for the big catch: aaron.
he gets aphmau to bring him to the cottage on the cliff just like normal: by saying she wants to introduce him to her brother. so he goes with her, and ein reveals himself and so on.
only this time, ein has no reason to want aaron dead, since he's not jealous of his relationship with aphmau. in fact, he very much needs him alive, so that he can turn aphmau. but obviously, he's not going to do it willingly.
ein knows that aaron's ultima abilities will activate if he's in mortal danger, as a hind brain defense mechanism to keep himself safe and alive. so he needs to get aaron to be on the brink of death, but still alive, so that he can turn aphmau whether he wants to or not.
and with this in mind, he gets aphmau to snap off a lock of aaron's hair, and thus gives her the potion to make her despise him, and the knife, telling her to make him hurt, but not to kill him; they need him alive.
so she chases aaron outside with the knife, slashing at him and backing him towards the cliff, while he's unable to fight back because he doesn't want to hurt her.
they're right at the edge. he's trying to talk her down-- she won't listen. she holds him close, and stabs him in the stomach, putting him in enough pain for his powers to manifest. he doesn't even notice: he's in too much physical pain and mental distress for the change to register, and aphmau looks him right in the eyes, sealing her transformation. she lets him go, and as she collapses he stumbles back, and falls off the cliff.
ein, waiting just behind them all this while, scoops aphmau up out of the snow, carrying her and soothing her as she screams and writhes in pain, bringing her inside the house to care for her as she begins her transformation.
