Devee

Devee's irregular genetic code allows her to evolve into any of eight highly distinct, advanced forms. The problem is she can't hold that form for more than a few hours at best. Once her energy runs out she devolves back into being just another small Eevee. Even stranger are the methods of evolving as just coming into contact with the appropriate stone isn't enough. The particular stone needs to be inside her body, swallowed or otherwise. Some people get weird ideas on where to put that stone...

Evolving into a new form does more than change Devee's powers. Each new body comes with a different personality. Devee still has all of her memories, but the person the eevee hugged might find the glaceon giving a cold stare. Even more bothersome is her attitude about vore. As an eevee she's happy to do whatever might be asked, like being devoured alive. Some evolutions of Devee would much rather be the predator, soon turning the tables on whomever provided the means to evolve. And if personality changes weren't enough, Devee's gender can sometimes shift as well during evolutions. Most trainers who discarded Devee complained that working with her was like trying to manage nine different pokemon all at once.

Devee still very much wants to evolve, and stay evolved. She'll try anything to make it work, especially if it makes someone else happy. Of course when it doesn't work Devee just smiles and carries on because there's always next time.