Werewolf Vi AU
So it starts with Marcus taking the Mad Chemist to Stillwater, where Vi "dies" after being injected with the Serum. She is taken out and buried, but then she comes back as a werewolf with reddish pink fur, the same color as her hair. Her mind is hazy after transform, but she knows she must get to Powder. However she has to get through Piltover, and when the enforcers spot her she climbs a fence and hides in some bushes, where she accidentally falls asleep. These bushes are on the Kiramman estate, and Caitlyn is the one to find her. This is set a few years after the explosion, so Vi is eighteen and Caitlyn is nineteen.
Caitlyn recognizes that Vi isn't a wild animal, and is intelligent, so she starts helping her, hiding Vi from her parents. This goes on for a few days, with Vi stuck as a werewolf, until the night of a storm. Caitlyn sneaks Vi into her room to keep her warm and dry, and the two end up falling asleep on the bed together. The next morning, Caitlyn wakes up to find she's spooning a very hot, very muscular, very tattooed, and very naked Vi, who is mostly human. They freak out at first, but eventually calm down and start to talk, while Caitlyn provides Vi some clothes.
The way Vi's new abilities work is that she'll transform into her werewolf form when feeling some intense emotion, such as rage, grief, terror, love, and so forth. For her to transform back, she has to calm down. The reason it took so long for her to change back the first time is because until Caitlyn brought her back to her room, she was in a constant state of fear and anxiety. But lying in bed with Caitlyn and hearing her sleeping peacefully finally helped her relax.
When Vi is in her human form, she isn't fully human. She has wolf ears and a tail, and she has captain america superhuman strength and durability. Her senses are also enhanced, she can see in the dark, track through smell, acute hearing, things like that. She has strong instincts as well, which help her fight. She also has a minor healing factor, not like wolverine or deadpool levels, but enough that she can shrug off any minor injury and recover quickly from major ones. When she's in her werewolf form, all these powers are dialed up to eleven, but her now extra strong instincts make it hard for her to make complexed plans and such. Also, as the serum came from Warwick, and included some of his DNA, another change is that Vi has a certain something that guys use to make babies between her legs. I'm including this so that Vi can have puppies with her cupcake, and they will be adorable. No smut though, as I don't write smut, but if one of you want's to do something with that you can.
Vi and Caitlyn will start working together to expose both Marcus and Silco, as well as save Powder, who is only thirteen and hasn't yet become Jinx or started doing jobs for Silco, though she does build things for him. They will also find Warwick, and there will be an emotional yet cute moment between Papa Wolf and his pup.