I was watching anime (don't remember which one, maybe Madoka Magica) and was thinking during a transformation scene that there should be something like that in D&D, so that was my main inspiration for this class, though heavily toned down. I wanted it to seem somewhat paladin-like, but without the spellcasting component. I might end up adding a subclass that has spellcasting to round out the subclasses, though, I've been having trouble coming up with a third subclass idea.
How is the playtesting going in your campaign? Are you the one playing the class or is it someone else? Does it seem stronger or weaker than classes with similar features most notably barbarian, ranger, and rogue?
Taking in the feedback as well as my own observances from DMing with a player running this class, I have finally revised it, and added a third subclass as well! Thanks for your feedback, and any more feedback would be greatly appreciated!