Fall of Sanctia
The battle began when the Ecclesiarchy world of Sanctia was assaulted by a warband of Orks which bizarrely consumed the planets defenders and inhabitants, both living and dead, as if compelled by a Daemonic hunger. The Orks soon became bloated monstrosities capable of only moving slowly, allowing the Adepta Sororitas to systematically purge the xenos. However it was at this point that the Primarch and Daemon Prince Mortarion, at the head of the Death Guard, struck. Making planetfall, Mortarion has the deceased but bloated Ork corpses explode, revealing their interior to be filled with many Nurglings. The Death Guard and Daemons of Nurgle sweep across the rest of the planet with their Primarch at the helm within only twenty hours. Mortarion went on to spread the plague across the greater Ecclesiarchy-held system at an unstoppable pace.