One of the most famous Inquisitors currently active and one of the most controversial, Eisenhorn began his career in the Ordo Xenos until his encounter with the alien Warp-grimoire known as the Necroteuch brought him onto the trail of the corrupted Inquisitor Quixos. Eisenhorn pursued and unmasked the deranged Inquisitor, finally killing the traitor in single combat.
That was many years ago, however. Once respected, even lionised, Gregor Eisenhorn has himself drifted into Radicalism within the Ordo Malleus, and exists only in the fringes of Imperial society. He is known to consort freely with the Daemonhost Cherubael, an entity he once considered a mortal enemy, and is believed to have added Warpcraft to his already formidable psychic gifts. His fellow Inquisitors now wonder if his agenda, whatever it may now be, is leading him to become every bit the danger that Quixos once was.