Marius Gage

Marius Gage was the First Master of the Ultramarines, a senior officer of Roboute Guilliman’s Legion at Calth and later Master of the First Chapter. He is recorded among the loyalist commanders of the Battle of Calth in 007.M31, alongside Guilliman himself, the Tetrarchs Eikos Lamiad and Tauro Nicodemus, and Captain Remus Ventanus. His rank made him one of the few officers to whom the primarch could delegate the running of the Legion’s wider muster, in which twenty of the Ultramarines’ twenty-two Chapters were gathered in the Veridian system on the Warmaster’s orders.

When the Word Bearers turned on their hosts at Calth, Gage was among the command staff around Guilliman on the flagship Macragge’s Honour, which the opening strike left crippled. Accounts place him in the fighting that followed, and one tradition holds that he lost a hand in the struggle against the Legion’s attackers and daemonic allies. Sergeant Aeonid Thiel, who is recorded on the same side in the battle, is sometimes linked with these events, but the details are not consistently reported. The battle ended as a costly loyalist victory. The Word Bearers’ invasion fleet, including the flagship Infidus Imperator, was destroyed, but the Ultramarines lost most of their fleet and a large share of their Astartes. The Underworld War beneath Calth’s surface then kept the Legion occupied until 014.M31, so it could not march on Terra. For the Ultramarines this made Calth a test of command as much as of arms: officers such as Gage had to keep a Legion functioning after the loss of its ships and much of its planning apparatus.

After the Heresy, the Codex Astartes divided the Legion into separate Chapters. Gage is recorded as the Master of the First Chapter, and later tradition gives him the title Chapter Master of the Ultramarines, the successor formation to the undivided Legion. The First Master title he held at Calth referred to the Legion’s command structure before the reorganisation. The Chapter Master title reflects his place within the new arrangement, which was governed by the Codex. His fate is not firmly recorded, and Orrery lists his status as missing. On the map he is bound to Calth in the Veridian system, where the war began, and to Macragge, the Ultramarines’ homeworld and the seat of the Realm of Ultramar. On the timeline his service falls within the Horus Heresy, at the Battle of Calth and the Underworld War, and the Legion’s later reorganisation.