Leonid Kravos

Leonid Kravos is a human sorcerer. He becomes known as the Nightmare after his death. He first appears in the novel Grave Peril.

Biography
He was captured during a raid of the warehouse that served as the headquarters of his cult. He attempts to summon a demon which is killed by Michael Carpenter. He later committed suicide in his jail cell before his trial and returned as the Nightmare.

Grave Peril
In Grave Peril, Susan Rodriguez asks Harry if he recalls the name of the guy that he and SI took down a couple of months earlier—the ritual killer. He reaches for the name saying Leo something, Cravat, Kraven or something. Harry had tracked him down through the demon he called up. Harry never really heard the name. Susan then asks if it was Kravos, Leonid Kravos, and Harry agrees that was it. Susan says she's just working an angle.

Later, Harry has a dream that recalls how he, Michael Carpenter and the S.I. team took him down during a raid of the warehouse. Then the dream changes to an entirely different horrifying outcome in which the team is overtaken by the demon—Azorthragal—that Kavros summoned up and takes a huge bite out of Harry.

See the Nightmare for more events.

Michael brought Lydia to Harry's apartment; he recognized her from Kravos's lair. When Lydia wakes up, she is posessed by the Nightmare. Michael can not slay it with Amoracchius because its inside Lydia—an innocent—not a construct (this would undo the Sword). Just as Harry is about to die, he finally realizes that Lydia is possessed by Kravos's ghost not his demon and knows how to destroy it. Thomas distracts Lydia by using his White Court–House Raith powers. This frees Harry to excorcise Kravos's ghost from Lydia.

Later, locked in a room at Bianca St. Claire's mansion, Kavros inhabits Justine and taunts Harry. shortly after, Harry sets a trap for him, goes to sleep, Kavros enters his mind, Harry dies, creates a ghost and destroys Kavros, eating back his powers and some of Kavros as well. Susan had been keeping his body going with CPR. After that, Harry was strong enough to escape their prison taking Susan and Justine with him.

Summer Knight
In Summer Knight, Murphy is having continual bad dreams—night terrors—about what Kravos did to her. What scares her is that there wasn't anything she could do to stop his invasion of her mind.

Ghost Story
In Ghost Story, Harry warns Murphy that with Mortimer Lindquist having been abducted by the Grey Ghost, he's not around to keep the Lecter Specters—serial killer ghosts—calm and happy which means they'll revert to being killers able to manifest. They could end up with many serial-killer ghosts like the Nightmare (Kravos) rampaging around Chicago killing. They need to rescue Morty. Harry considers that if Kravos had access to his magic as a Ghost that it stands to reason that he should as well.

Cold Days
In Cold Days, the Summer Lady, Lily, implied that the Contagion—later named Nemesis—corrupted Harry's first three big cases: Victor Sells the Shadowman, Agent Denton and his Hexenwolves, and Leonid Kravos the Nightmare.