Necromancy is a field of magic that involves the manipulation of life and death. While necromancy can be greatly beneficial - healing injuries, for example - it is better known as the form of magic that allows for the raising of the undead and the manipulation of souls.
Most, but not all, cultures on Kishar hold strong prohibitions against the latter form of necromacy, usually for spiritual reasons. This is not universal, however. Some peoples, like those of Talgazan and old Razgovir, tolerate specific strains, specifically viewing that which that involves calling forth and communicating with ghosts quite positively. Certain other peoples have no issues with necromancy at all, though this tends to be somewhat rare.
Spells and rituals that raise and bind the undead consume vast amounts of onyx as a magical component.