Pacification of Mavros

The Pacification of Mavros was an Imperial excoriation campaign conducted by the fierce and unforgiving Iron Spears Space Marine Chapter against the formerly Loyalist Angels Vigilant Chapter that were declared Excommunicate Traitoris by the High Lords of Terra.

Background
In 236.M39, the population of the planet Mavros, home world of the traitorous Angels Vigilant Chapter, attempted to secede from the Imperium. During the Mavros Revolution the Angels Vigilant had entered a state of radio silence, never responding to any transmissions from the greater Imperium. The Iron Spears were sent to quell the rebellion and investigate the radio silence. When they arrived on Mavros they discovered temples, shrines, altars, and effigies built to honor the Chaos gods.

As they cut through the hordes of cultists and reached the Angels Vigilant Fortress-Monastery, the Loyalists were assaulted by a unit of Death Company Marines bearing the Mark of Khorne. In the midst of the skirmish the rest of the Angels Vigilant Chapter (now known as the Void Stalkers) emerged, revealing that they had fallen to chaos, and that this renegade chapter was the mastermind behind the planetary secession. After a long and grueling battle against the Void Stalkers and their waves of chaos cultists, the Astartes forces were forced to resort to Exterminatus. However, some of the Angels Vigilant escaped the planet aboard a lone Battle Barge and fled into the Eye of Terror.