Lycanthropy

When most people think lycanthropy they think of werewolves, though many creatures such as bats, rats, bears, and even tigers can come in lycanthrope forms.

Each one has unique abilities based on what kind of animal the lycanthrope form takes, but they do share a few things in common.

For starters, they are all affected by moon phases. Contrary to popular belief a lycanthrope can transform at any time, day or night, but they are at their least powerful during the daylight and new moon and most powerful during full moons.

Secondarily, most do maintain control when shifting into a lycanthrope form. Though the more power they wield the harder it is to keep control, and once it's lost it's very hard to regain. In fact most don't, they work themselves into a frenzy and end up getting killed by others defending themselves from what, at that point, is little more than a crazed animal.

Third, places that lack moon phases are where lycanthropes are at their weakest. Certain fey realms, for example. In fact in some such realms a long enough stay can even cure one from their lycanthropy...or so they say, at least.

And fourth, lycanthropy can affect almost anyone. A few extremely powerful individuals are totally immune, but it is a curse not a disease so Paladins and the like are not immune to it. There are several cures in the form of potions and spellwork and the like, though the longer one has been inflicted the harder it is to cure and those born with it cannot be cured at all.