Aurora Chapter - Eukari Insurrection: Sometime in 330.M41, there arose a destabilisation of relations between both the Aurora Chapter and their fellow scions of Guilliman -- the Emperor's Spears Chapter. Many Successor Chapters hold little affinity with their genetic forebears, but the Emperor's Spears are a key example in the rare cases of a Chapter detesting one of its kindred bloodlines to the point of coming to blows. In this instance, it was over a matter of honour.During the Eukari Insurrection, a strike force of Emperor's Spears came into conflict with a vanguard of warriors from the Aurora Chapter, a close-bound descendant of the noble Ultramarines. However, the Emperor's Spears' 4th Warhost arrived to find the insurrection was already being fought by the Aurora Chapter -- technically a cousin bloodline to the Emperor's Spears.Rather than greet the Emperor's Spears as brethren, the commander of the Aurora Chapter berated the Spears for requiring other warriors to fight their wars inside Elara's Veil. With typical hot blood, the Emperor's Spears replied with a planetary deployment right into the heart of the enemy capital, sustaining heavier losses than the Aurora Chapter's meticulously fought counter-offensive, but stealing all glory of the victory for themselves through three solar days and nights of brutal urban warfare.With the Chaos warlord's still-bloody skull chained to his pauldron, the lord of the 4th Warhost -- Captain Trystance of the Arakanii -- voxed the Aurora Chapter commander and informed him that his warriors had no right to mark the battle on their war banners as a victory, since the Emperor's Spears had "done all the hard work."The exact events that led to continued destabilisations in the Chapters' relations are unclear, though it seems both commanders eventually agreed to an honour duel to end the unrest. Even this engagement is the source of yet more conflict, as both Chapters claim their champion was victorious, and in the skirmish that followed, both Chapters claim the other side fired the first shot that led to several warships sustaining significant damage in the name of Adeptus Astartes pride.A group of representatives from the Ultramarines, acting either as benevolent overseers or unwanted judges depending on which Chapter's perspective is being described at the time, later ruled in the Aurora Chapter's favour. They stated that the Emperor's Spears had acted according to rash, impulsive instincts rather than following the approved guidelines for multi-Chapter warfare laid out in the Codex Astartes and that the glory of the victory was to be equally shared.Such was the bitterness that arose over the Ultramarines' perceived inflexibility (some archives list it as "favouritism") that Trystance of the 4th Warhost swore never to set foot on Macragge even if the planet was imperiled by threat of destruction.No record exists of the Emperor's Spears and the Aurora Chapter fighting together since the event, though there is an apocryphal tale in the Liber Honora Astartes Quintia that says a cargo vessel arrives every ten standard years in the skies above Firestorm, homeworld of the Aurora Chapter, "declaring that it brings a tribute to the Spears' 'beloved cousins.'"This gift is the same each decade: the ship has a hold full of seawater and several hundred abyssal vine-serpents, supposedly a despised -- and incredibly ugly -- breed of oceanic vermin on the Emperor's Spears' homeworld of Nemeton, with no nutritional value whatsoever and a profoundly unpleasant taste.