The fall of Hemera

While the Imperium were distracted with their own schisms and the alliance on the eastern fringe, more and more resources were drained from the already tenuous Imperial possessions in the Perseus Deeeps. By late 016M42 the imperial garrison on Hemera had already put down several "populist risings", only to find in early 017M42 that a genestealer cult, a vanguard tendril of Hive Fleet Nemesis, had taken over vital installations and declared itself the new government.

In response the Space Wolves and Darrantine Guard were dispatched by Sector Commander Titus Luthor. However when they arrived the imperial forces faced frenzied attacks, not just from cultists but purestrain genestealers. Days of protracted fighting became a desperate holding action as the xenos forces overran the imperial forces and beseiged the only way off the planet, the imperial spaceport.

The small colony received unexpected aid from the eldar, who appeared from the webway to try to reverse the tyranid gains. It was to no avail and the eldar, of the recently discovered "Ynnari faction", were soon overrun themselves and found themselves fleeing into the webway. They never made it to the besieges imperial forces, and all but a few astartes were massacred in the final moments of Hemera's fall.