Wereraven

An incredibly powerful 'disease' that is more of a blessing than a curse. Although lycanthropy in general can lead to loss of control, when the raven mind takes over the afflicted is more likely to steal shiny objects of dubious value rather than maul anyone. In addition, controlling the curse is a fairly simple process and once the curse is under control the afflicted is in complete control even when the moon is full and they can't avoid the transformation. Plus, they are able to turn into bird or hybrid form whenever they want. On top of that, while they are in non-humanoid form, i.e. bird or hybrid, they gain health regeneration as long as they aren't attacked with a spell or silver weapon. They also gain claw and bite attacks in hybrid form, but admittedly they are not likely to be as powerful as weapons and spells the character already has.