Alaxxes Nebula

The Alaxxes Nebula is a stellar region of dust and ionised gas named in Horus Heresy accounts as the site of the Battle of the Alaxxes Nebula in 007.M31. No segmentum assignment, sector or galactic coordinates are attested for it, and it is not recorded as part of any Imperial administrative division.

The nebula’s dense media scatter sensor returns and make detection unreliable, conditions that favour concealment and ambush over open manoeuvre. Those properties shaped the one engagement for which the region is known. After the Burning of Prospero, Leman Russ’s Space Wolves, depleted by unexpectedly heavy losses on that world, were ambushed by a large Alpha Legion fleet and driven into the nebula, where they were surrounded and besieged. Jaghatai Khan, receiving Russ’s call for aid together with a message from Horus naming Russ the traitor, declined to intervene and made for Prospero instead.

Within the nebula the Space Wolves attempted a breakout under First Captain Gunnar Gunnhilt, who gave his life and his ship Ragnarok in destroying the Alpha Legion battleship Delta. Russ is recorded as fighting Alpharius, disguised as one of his own Lernaean Terminators, in the closing stage of the battle. Relief came from the Dark Angels star fort Chimaera under Chapter Master Althalos, whose intervention forced the Alpha Legion to withdraw and allowed the surviving Wolves to set course for Terra.

No settled population, garrison or later Imperial administration is attested for the Alaxxes Nebula, and its status after the Heresy is not recorded. It survives in the record chiefly as the theatre of that engagement between the VI and XX Legions, in which the Space Wolves were nearly destroyed on their way back towards the Throneworld after Prospero.