Also known as demons, mutants, and monsters, Youma were once human beings.
Strange creatures, half dreamed half imagined, figments of delerium, wisps of insanity.
Magic should have side effects, both expected and unexpected - fortuitous and deplorable. Expected side effects add anticipation, while unexpected ones increase the drama of the scene. The result can be comedic or dire, it dpends on which circumstances work best for your game.