Eisenhorn is a series of novels and short stories by Dan Abnett, following the adventures of Inquisitor Gregor Eisenhorn. It originally debuted in 2001 alongside the release of Games Workshop's 54 millimetre model RPG game, Inquisitor. Eisenhorn was a named character in the game with his own model, as was his antagonist and ally, the Daemonhost Cherubael. No other characters from the game appear, but the types of characters in the game -- Arbiters, Rogue Traders, Deathwatch Space Marines, savants, Mechanicum Magi and so on, are featured as key characters in the series. Inspired by these and the content of the game, Abnett wrote the initial trilogy, with Xenos, the first novel, released at the same time as the game.