Lycanthropy

The were-creatures hold their origin from the beastkin, when somebody through magic tried to get rid of their beastman nature long ago, they thought they had gotten rid of it, but instead they had become a were creature, they split themselves into a normal looking human and a savage beast that builds up until it bursts, and even worse it spread. It's also incredibly difficult to cure. it also passes on biologically, if 1 of the 2 children is a werewolf then the child is. It is a nasty condition. It is not impossible to control the inner beast, but it is notoriously difficult. There are also those who let themselves get swallowed by it, they are seen to lose themselves and become nothing more than savage beasts in both forms. triggering the were form outside of a full moon is also possible with training, as in reality what it needs is a specific life energy tick that the moon gives, so things like being in a magically ambient strong areas, emotion or a monk like training, can also trigger it or come closer to triggering it. like a lot of magic abilities with practice a lot is possible.