Necroscope

Necroscope is a horror novel by Brian Lumley, published in 1988. Its central character, Harry Keogh, can speak with the dead, and the dead tell him things that the living have no way of knowing.

What they tell him is that a master vampire named Thibor Ferenczy lies trapped between death and life in the mountains of Romania, bound by earth and silver, and that he is looking for a way out. He has found one in Boris Dragosani, an agent of a secret Russian service who has ambitions of his own.

Ferenczy teaches Dragosani the skills of a necromancer, including the ability to tear secrets from the minds and bodies of the dead. Dragosani means to use what he learns to rule the world rather than to serve his teacher, and the novel brings the two of them and Keogh into the same struggle, with the dead caught in the middle of it. Keogh's ability is the counterweight to Dragosani's, because the same dead who speak to him can be made to speak for the other man.