Necromancy1 is a form of divination magic which involves calling up and consulting the spirits of the dead, either about information they knew in life or because the dead are thought to be outside time and therefore know the future as well. In some cases - mostly fantasy fiction and fRPGs - necromancy is blown out into a larger school of magic that, ironically, involves very little divination and is more concerned with the undead - creating them, controlling them and aping their powers. Those with more respect for etymology may well call this expanded brief thanaturgy2 In some settings necromancy (or thanaturgy) may also have other 'dark' (and not so 'dark') functions to do with the manipulation of life generally - often these are about death and disease, but in some cases they may include biothaumaturgy and other forms of grim medicine.
Necromancy is generally considered black magic or left-hand path working - indeed it is one of the forms of magic explicitly forbidden in The Bible4 - and this, as much as the general squick of messing about with corpses, leads to most depictions of the necromancer as either a monster or a madman.
This is not necessarily the case - in a culture that practices ancestor worship or shamanism necromancy (in its strictest form) should be a lot more acceptable … indeed the undead bothering version may be acceptable as well to some cultures that can tolerate a 'walking ancestor' hanging about. The earliest literary depiction of necromancy is probably in the Odyssey when Odysseus calls up the spirits of the dead for information concerning his route home. The Bible gives a less positive portrayal to King Saul's contracting a witch to summon up the ghost of the Prophet Samuel in 1SAM28:3-25, but then the Greeks had no absolute religious prohibition about bothering the dead.
Where necromancy is considered black magic, expect there to be fairly stiff penalties against it, possibly enforced by the secular powers, religious authorities or the wizard's guild. Or all three. In less clear cut settings those three power centres - and others - may disagree5.
In edgier settings, resurrection magic may be part of necromancy.
"You don't come to the dead for wisdom, Lennier. My head was cut from my body. Even now, it rots on a pole outside the Imperial Palace. Birds have taken the hair for their nests. Maggots ate my flesh. And you want wisdom?"
(the Ghost of) Mr Morden Babylon 5
Game and Story Use
- Having a necromancy tolerant society is a great subversion for PCs used to necromancers who are always chaotic evil. A setting where necromancy is normal even more so.
- The sort of setting in which necromancy is one end of a school which also enables magical surgery is also great for values dissonance - in order to understand life, a wizard must first comprehend death…
- The nature of necromancy may also affect its in game 'flavour' - does it drag spirits back from the afterlife and torment them, or does it entice them out with offerings? Are the dead always bitter and hateful towards the living6 or much as they were in life?