Hastur Sejanus

Hastur Sejanus was a captain of the Luna Wolves and a member of the Mournival, killed at Sixty-Three Nineteen during the Great Crusade. The Luna Wolves were the Legion later renamed the Sons of Horus, and the Mournival was the small council of senior captains that advised Warmaster Horus Lupercal. Sejanus is recorded as one of Horus’s closest companions, and his death is the event that opened a place on that council for Garviel Loken. He is a distinct figure from the General Sejanus who served in the Macharian Crusade some ten thousand years later.

Sejanus sat in the Mournival alongside Ezekyle Abaddon, Tarik Torgaddon and Horus Aximand, and was regarded as a favoured subordinate of the Warmaster. During the 63rd Expedition’s compliance action at Sixty-Three Nineteen, a world whose ruler styled himself the Emperor of Mankind, Horus sent Sejanus with a glory squad as his envoy. Accounts differ on the immediate cause: some record that Sejanus suggested there might be another Emperor, others that the ruler demanded Horus kneel. In either case the ruler’s guard, the Invisibles, killed the embassy. Horus is recorded as having felt the loss deeply, yet authorised a second approach under his equerry Maloghurst. When that ship was shot down, Abaddon made a final appeal, the Luna Wolves went to war, and Loken’s Tenth Company later took the palace.

Sejanus’s death made room for Loken in the Mournival, and the campaign that killed him is often read as an ironic forerunner of the Heresy’s last battle, in which Horus stood before the true Emperor. Later tradition holds that during the rituals at Davin, Erebus of the Word Bearers took the likeness of Sejanus to speak with Horus in the Warp, using the memory of a trusted friend to press the Warmaster towards rebellion. On the Orrery map his death is bound to Sixty-Three Nineteen, with Davin as the site of the later impersonation; on the timeline he belongs to the Great Crusade and the Mournival’s earlier membership, before the Isstvan campaign and the Siege of Terra involving his former companions.