"An Obscurial’s power is morphing into an Obscurus... which is largely an incorporeal, amorphous entity... they can’t be killed in that form... from that form they have the ability to transfigure into any living creature, magical or otherwise.... They are the purest form of Dark magic... They can keep the foulest creatures alive if fed on... but for a powerful Obscurus to exist to feed you, you need an even more powerful dark spell to control it... It is like trying to put a collar on pure chaos..."