Siege of Varak Fortress

The Siege of Varak Fortress was an Imperial castigation campaign carried out by both the Black Knights and Manticores Space Marine Chapters upon the hive world of Halis, that was embroiled in the brutal civil war. Upon arrival, the Black Knights' librarians detect the unmistakable spore of the Fallen, and proceed to track down their wayward foes. Once they make planetfall, they encounter their fellow Unforgiven Chapter - the Manticores. Working together, both Chapters deploy their elite 1st Company formations, captured three Fallen. They also successfully put down the insurrection, before departing with their prize.

History
While on routine patrol, the Black Knights intercept a call for aid from the Hive World, Halis. The planet is currently locked in a civil war, with one side being Imperial Forces, and the other being a collection of local Chaos Cultists enforced by Chaos Space Marines. Upon arrival, the Chapter's Librarians detect the unmistakable presence of their Fallen kin are leading the Chaos Forces, commanding them from Varak Fortress. Thus, the Black Knights' Inner Circle immediately despatches the elite Lion Guard and Ravenclaws Companies to capture their wayward foes. Upon arriving on the planet, they greet their fellow Unforgiven Chapter, the Manticores, who have also despatched their Deathwing, Ravenwing companies, as well as their elite unit, the Hunters Six. The two Unforgiven Chapters work together to put down the Chaos uprising, and later besiege the Varak Fortress, to route out the Fallen within. It is thanks to the Hunters Six that the fortress falls, as they sabotage its outer defences before capturing the three Fallen Angels. The Manticores give custody of the Fallen to the Black Knights, so that they may be judged, though the Black Knights give credit of the capture to the Manticores in return.