Karus Incident

The Karus Incident was a lamentable event that occurred in the history of the Invictors of Mars Space Marine Chapter when they were campaigning alongside two unnamed Successor Chapters of the mysterious Dark Angels. These three Chapters were in the midst of conducting a joint-campaign to retake an Imperial world that had fallen into open insurrection. In the midst of the initial assault, without warning, one of these Unforgiven Chapters turned upon the Invictors and began shooting at them, in what was, at first, perceived by the Invictors as an incident of 'friendly fire'. The Invictors immediately took cover until they could reassess the situation. Due to this incident, this instilled a mild hatred within the Invictors for all Chapters of the Unforgiven.

History
While on campaign, the Invictors fought alongside two Dark Angels successors. In the midst of the firefight, one of these chapters began shooting at their Invictors allies. Unsure if their actions were accidental or intentional, the Invictors all ducked behind cover so that they wouldn't be in their line of sight. After the fight was over, the Dark Angels Successor that fired upon them sent a captain as a representative, who informed the Invictors, "You disgust us with your existence," and then departed. This gave the Chapter a mild hatred for the Chapters of the Unforgiven as a whole.