Soul Magic

Soul magic is the practice of using souls to power magic. This is anathema to the extreme, destroying a soul in order to use its potent power to fuel magic is akin to killing a person in order to eat them. Anyone who practices this magic is often hunted as a monster, like vampires or most undead, feared by the common folk and hunted by the bravest and purest of warriors.

It is the most potent form of magic known to exist, and is expressly forbidden by most gods. There seems to be a strong barrier that prevents most magic users from stumbling into soul magic, it often requires immense talent and extensive study to even attempt such magic, let alone to control it without destroying yourself.