From Lexicanum

Urkrathos was on of the four Chosen of Abaddon and was selected to command the fleets of Chaos at the launch of the 13th Black Crusade. His flag ship was a Grand Cruiser originally named Ius Bellum during the Great Crusade, but once Horus had made his intentions known it was renamed the Hellforger.

Sources

• The Grey Knights Omnibus: Dark Adeptus (Novel)