Battle of Hollonan
In response to a request for assistance in putting down a seemingly minor rebellion, Chief Librarian Mephiston of the Blood Angels would lead a strike force to the Imperial Hive World of Hollonan. However what was first thought to be a minor rebellion was soon revealed to be a massive infestation by Tyranid Genestealers of a splinter fleet of Hive Fleet Kraken. Though they managed to purge the alien infestation, the Blood Angels were too late and the invasion of Hollonan by Tyranid Bio-ships was already underway. Realizing the gravity of the situation, Mephiston sent requests for aid to the Angels Vermillion Space Marine Chapter.
In the ensuing battle, waves of Tyranids managed to overrun both the planetary defense batteries and fusion reactors. Only where Mephiston fought did the forces of humanity hold in a vicious two-week battle. Managing to personally slay the Hive Tyrant, Mephiston himself was struck down by a Trygon in the process. As the battle seemed increasingly desperate, fresh companies of Blood Angels and Angels Vermillion emerged from the sky in Drop Pods and Stormraven Gunships. The forces of humanity were further aided by the Eldar of Ulthwe Craftworld under Farseer Eldrad Ulthran, which had chosen to temporarily ally with the Imperium for their own mysterious reasons. Caught between the 3 armies, the Tyranids were crushed. Eldrad remained just long enough to see Mephiston recovered from the rubble before the Space Marines and Eldar went their separate ways.