White Dwarf EoT campaign wrote:The hive world of Subiaco Diablo was the first planet in the Belis Corona sector to come under the heel of the forces of Disorder, as the Plague Marines of the Death Guard Traitor Legion unleashed their foulest contagions upon its populace. Soon, the shattered streets were home to the unquiet dead, the Plague Zombies of Nurgle, reanimated victims of the Plague God's choicest gifts. Throughout the opening phase of the invasion, only the convent of the Order of the Order of the Ermine Mantle held out, though at terrible cost, against the shuffling hordes of undead.

At the height of the invasion, something truly unexpected occurred. Defenders on the outlying systems reported contact with Tyranid organisms - at first individual vanguard-organisms such as Lictors, but soon entire broods of Genestealers and Hormagaunts. A splinter fleet of Hive Fleet Leviathan, a Tyranid fleet known to be attacking up through the galactic plane, was taking advantage of the mass destruction initiated by the invasion to gain a foothold in strategically vital Imperial space.

Faced with both the pustulant forces of the Death Guard, and the voracious hordes of Tyranids who were, unlike the human defenders, immune to the Plague God's blessings, the forces of the Imperium were hard pressed to defend the vital worlds of the sector.