7th Black Crusade

The 7th Black Crusade was a Black Crusade led by the infamous Chaos Champion Abaddon the Despoiler and his Black Legion, launched out of the Eye of Terror in 811.M37. Written within the The Canticle of Cassandria Lev - Vol. CVI is the eponymous Sainted Sisters' highly mythologized and oblique account of the wars of the 7th Black Crusade is found mention of a "grey-clad" Space Marines Chapter who came from "The outer night" to aid the Imperium, and whose "Jagged maw did swallow the stars ... " and whose " ... black gaze did mirror the void of oblivion". In the course of the canticle this Chapter's ships set upon Abaddon's forces following the disastrous defeat and routing of the Blood Angels Chapter at Midian and attacked the pursuing forces as Saint Lev writes: "...fell upon the servants of the skulled-one with great fury from the darkness, unseen as the beast that lurks beneath the black waters, death for death, blood for blood...thus were the Sons of Sanguinius bought respite, and did turn back upon their pursuers and so were the damned traitors of the false gods driven unto their ruin." Images of these events can be found upon the walls of the crypt-world of Hypasitis created to house the honoured dead of that war, depicted in repeated fresco and bar relief, but cuniously the faces of the intervening Space Marines there depicted are obscured with featureless disks of black obsidian. Given the largely unknown history of the star-faring Carcharodons Chapter, accounts of their activities can only be constructed from recorded historical incidents and fragmentary records that are believed to have involved the Carcharodons on balance of evidence. This notable engagement is listed by Imperial savants as a '[Special] Probable Encounter/Recorded Sighting' of this notorious Chapter.

Canon Conflict
There is some confusion as to where the attack by Abaddon and his Forces of Chaos against the Blood Angels actually took place. In Codex: Chaos Space Marines (3rd Edition, 2nd Codex) it states, "When the Blood Angels battled against the horde at Mackan, Abaddon singled them out with implacable fury." But in the recently released Imperial Armour Volume Ten - The Badab War, Part Two, under the Notable Campaigns of the Carcharodons Chapter, that the "...following the disastrous defeat and routing of the Blood Angels Chapter at Midian." One could assume that with the more recent release of the Imperial Armour book, that the more recent canon would likely place this notable engagement at Midian instead of Mackan.