|Spoilers: Crimson Death
This article or section contains spoilers for 2016 novel Crimson Death.
Proceed with caution.
Necromancers have an inborn ability to control the dead. They can raise zombies easier than animators, and sometimes don't even need an animal sacrifice. They usually also have some control over vampires. In the daytime they can animate a vampire's corpse, whilst it is soulless. Later in the series Anita grows in power enough to have some control over vampires even while they are alive, in nighttime. All necromancers have the potential to be able to control all flavors of dead, if they grow powerful and skilled enough to do so, but most never do.
Marmee Noir, one of the first necromancers and a vampire/lycanthrope, ordered at some point in time the hunting and destruction of all necromancers, for fear that they could eventually gain control over vampires.
Anita is one of the most powerful known necromancers, but her control is mostly "natural instinct". She can raise zombies that are centuries dead without human sacrifice, and can make them look lifelike. She can "heal" any sign of decay or injury in the corpse. In Bloody Bones and The Killing Dance she raises vampires (during daylight) as if they were zombies. According to Jean-Claude, this is a rare ability. After raising a vampire, she can heal any wounds as if it were a zombie and can control them; in Blue Moon, she realizes she has some measure of control over Damian. In Affliction Anita is able to raise entire cemeteries at once to create herself an army of zombies. In Dead Ice Anita learns she can also control ghouls, up to a point, and in Crimson Death she manages to weaponize ghosts.
Although not as powerful as Anita, Dominic has had centuries to learn and practice necromancy. Using his knowledge of rituals and spells, he creates a spell to save his master from the affliction that is making his body rot. He also sacrifices Robert, in order to take his heart, a necessary "ingredient" for the ritual. (The Killing Dance)
Larry is powerful enough to be a necromancer in his own right, but his strict morals and squeamishness limit his ability to actually harness the power. He is prejudiced against necromancy and sees himself as just an animator, and isn't thrilled when he realizes the various European authorities don't agree with his self-classification. That helps him get over some of his issues with Anita in Dead Ice, but it's unclear whether it affects his attitude towards his potential abilities.
Manny says he used to be a necromancer, back when he was also a vaudun priest, but he doesn't seem to consider himself one anymore. Dominga Salvador says he could have been very powerful, but in the end he didn't want the power and left that life behind.
The Mother of All Darkness is one of the first necromancers ever born (or at least recorded), and has gained an enormous amount of power through the millennia. It's unclear which of her gifts are born out of necromancy and which from her vampirism, or whether there's much practical difference between the two.
Probably not a born necromancer, but gains at least some of the abilities after swallowing what power is left over when Anita kills Marmee Noir. (Crimson Death)
Probably not a born necromancer, as he is initially known merely as a rotting vampire who can feed on death, but after allowing Marmee Noir possess him he is able to use her power to raise an army of flesh-eating zombies out of regular corpses, and even from bodies that haven't been buried yet. (Affliction)