Rebulus Cleansing

The Rebulus Cleansing was a joint-Imperial castigation crusade carried out by the Black Knights Space Marine Chapter, alongside their progenitors the Dark Angels and several other Unforgiven Chapters, to purge the rebellious Rebulus System of Chaos-corruption. This brutal and bloody campaign would last three decades, resulting in nearly a dozen worlds cleansed of the taint of the Ruinous Powers and several Fallen captured.

History
Following a mysterious trail, the Dark Angels and several of their Successor Chapters - including the Black Knights - begin a 30-year campaign that uproots hidden cults and corrupt officials across three sectors of Imperial space. The battles against this network of subversion bring much suffering to the Rebulus System before the corruption is finally subdued, culminating in the destruction of the artificial moons surrounding the planet Ixx.