Necromancers can raise the dead and control the dead, because they have an affinity for all types of dead. When made into human servants, they are very powerful. At one time Vampires killed necromancers on site.
Necromancers appear born with the power, and it may blossom at puberty.In the series, at 13, Anita inadvertently raised her dog from the dead 3 days after it had died.
Necromancers need to learn how to control and focus the power. Uncontrolled powers can be embarrassing. They can have the same effects of accidentally raising the dead without even being aware of the fact until the newly raised zombie comes to them.
Again, in the books Anita's Grandmother Flores, a vaudun priestess, began teaching her how to control powers. However since her powers were escalating they frequently out run her ability to control them. Though training and use these powers strengthen. Anita describes her first observing Larry Kirkland in Circus of the Damned thus:
The magic built on the air until it pressed against me like a weight. It was hard to get a full breath. His magic rode the air, and it was strong, but uncertain. I could feel his hesitation like a touch of cold air. He would be powerful, but he was young. His magic tasted untried, undisciplined. If he wasn't under twenty-one, I'd eat my hat. That's how Bert found him. He was a baby, a powerful baby. And he was raising his third zombie of the night. Hot damn.
~ Circus of the Damned ~
When Anita uses her necromancy powers, they feel like a cool wind that emanates from her body. It's as if all her nerve endings are raw, naked to the wind. She creates a circle of wind that can sift through the dead bodies in the ground and sense them. She can also act as a focus, combining her powers with another necromancer. With Larry, however, this quadruples the power rather then doubling it.
Dominic Dumare was a necromancer who was also the Master Vampire Sabin's Human Servant. Dominic offered to teach Anita the art of necromancy because he could sense in her the raw power. Power is part of what makes a good necromancer; the other part is the knowledge of how to use that power.
Nicandro Baco, Nicky, is a Brujo (witch), the vargamor of the Los Lobos Clan. A werewolf pack out of New Mexico. He was also a Necromancer. He used his powers in order to punish the members of the Los Lobos Clan. He drains their bodies and then fuses them into a creature known as monstruso. There are at least 40 heads on the thing. Anita is the only one who realizes that they are not dead, since their souls are imprisoned in the creature.
Vampires and Necromancers
It was standard practice long ago for vampires to kill Necromancers on sight. With good reason. Powerful Necromancers are able to raise the slumbering corpse of a vampire as if it was a zombie. Moderate Necromancers and Animators cannot do this. Something in the vampires system that makes them what they are prevents this. Necromancers with enough power are able to circumvent this and raise the vampire anyways. Once raised as such, the vampire becomes under the complete control of the Necromancer, even after the corpse is put back and the vampire rises at sunset.
Necromancers also have the ability to mark a vampire. Just like a Master Vampire would do to a human to make them a Human Servant. Vampires do not like this because they are under the complete control of the Necromancer and are forced to obey every command given to them by their new Master or Mistress.