I thought necro had something to do with being dead. So, what's a necromancer? Sounds creepy.

Necromancers claim the power to communicate with dead people, a feat they achieve by conjuring up the spirits of the dearly departed. Through their sorcery, necromancers believe they have a ghost of a chance of predicting the future through the secrets shared by those raised from the dead.

From Nathaniel Hawthorne's The Scarlet Letter:

Others contended that the stigma had not been produced until a long time subsequent, when old Roger Chillingworth, being a potent necromancer, had caused it to appear, through the agency of magic and poisonous drugs.

And in A Connecticut Yankee in King Arthur's Court, by Mark Twain:

But it never occurred to one of them to reflect that if I was such a wonderful necromancer as I was pretending to be, I ought not to need salves or instructions, or charms against enchantments, and, least of all, arms and armor, on a foray of any kind — even against fire-spouting dragons, and devils hot from perdition, let alone such poor adversaries as these I was after, these commonplace ogres of the back settlements.

From Charles Dickens's Bleak House:

For it is, even with the stillest and politest circles, as with the circle the necromancer draws around him — very strange appearances may be seen in active motion outside. With this difference, that being realities and not phantoms, there is the greater danger of their breaking in.