Castor Alcade was a Legate of the Ultramarines during the Great Crusade and Horus Heresy. Commander of the 2nd Battlegroup of the 25th Chapter, Alcade was a major Imperial commander during the Battle of Molech. As the battle raged, Alcade and his men eventually encountered Alivia Sureka and learned of her effort to prevent Horus from gaining the powers of tehe Emperor through Molech's Warp Portal. Alcade and his men gave their lives holding the line against Horus' Justaerin at the foot of the Warp Gate. Alcade himself was killed by a single swipe of Horus' Power Maul.