Event · M31

Muster at Ullanor

The Muster at Ullanor was the gathering of Traitor Legions on Ullanor in the later Horus Heresy, summoned by Warmaster Horus Lupercal in preparation for the drive on Terra. It followed Horus’s consolidation of the traitor war effort after the earlier Triumph at Ullanor of the Great Crusade, at which the Emperor had named him Warmaster, and is distinct from that victory celebration. Magnus the Red reappeared at the head of an army of Thousand Sons to answer the Warmaster’s call, having restored much of his strength by the recovery of shards of himself after the Burning of Prospero. The muster assembled the principal Traitor Legions and their allies for the final advance on the Sol System. Accounts of the order of arrival and of the councils held on Ullanor differ in detail, but agree that Magnus stood among the primarchs who committed their forces to Horus’s plan. Shortly before the Siege of Terra, Magnus and Ahzek Ahriman journeyed from this concentration of traitor strength to the ruins of Prospero to recover the daemon Shai-Tan for use against the Emperor’s psychic shielding of Terra. From Ullanor the traitor host moved on the Solar War and the Siege of Terra. The muster therefore links Magnus’s return to material command of the Thousand Sons with the Heresy’s closing campaigns, and seats Ullanor as the staging world of the drive on the Throneworld rather than solely as the site of the earlier Crusade triumph. Perturabo brought the Iron Warriors to the muster after an errand on Horus’s behalf. Ordered through the emissary Argonis to find Angron and bring the World Eaters to Ullanor, he left much of his Legion holding the line against the advancing Ultramarines, learned at Sarum that Angron was on Deluge, and subdued the daemon primarch there with the aid of the Iron Circle and his warriors. When an Ultramarines fleet arrived over Deluge, Angron raised a warp storm that carried both Legions’ fleets to Ullanor, where they joined Horus’s host for the drive on Terra.

See where Muster at Ullanor occurred on the galactic map during the Horus Heresy.

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