In the backdrop of the greater Macharian Heresy, the civil war within the territories conquered by the now-deceased Lord Commander Solar Macharius, the battle began when the Doom Warriors and Inceptors, formerly allies in the Macharian Crusade, had come to blows over a matter of honor and were embroiled in a protracted conflict in the Euxcine System. Seeking to end the conflict, Imperial authorities dispatched the Minotaurs to handle the matter. Caring nothing for the causes or rights of the two warring chapters, the Minotaurs attacked both in full force.
The Minotaurs were successful and caught both forces unprepared, decimating them in their initial strike. Over-matched and broken, the Doom Warriors fled the system in a rout. The Inceptors meanwhile were encircled and slowly destroyed piece by piece, until the last remaining Inceptors Space Marines were forced into a humiliating surrender. Fewer than a hundred Inceptors survived the Euxcine incident, while the Minotaurs confiscated many of the Chapters relics and took their Battle Barge flagship as their own. The Minotaurs arrogance and brutality against an honored chapter with close ties to the Ultramarines sent shockwaves throughout many Space Marine chapters, especially given the tacit agreement the Minotaurs had with the High Lords of Terra. The Minotaurs were denounced across Ultramar for their "Atrocities" and were forever forbidden to enter its territory. Other Ultramarines successors have since sworn vengeance against the Minotaurs should the opportunity arise.