Attack on the UNSC Orphellion

The Attack on the UNSC Orphellion was an engagement between the UNSC and the Promethean forces of the Created onboard the UNSC Orphellion. While fleeing from Human controlled space due to the arrival of the Guardians, it was suddenly dropped out of Slipspace by its A.I., Amycus, who was revealed to be a member of the Created. Shortly after, Amycus summoned a pair of Forerunner ships, which began teleporting Promethean forces aboard in an attempt to "pacify" the ship's crew. While the majority complied with the A.I. and Prometheans, the ship's Spartan and Marine contingent refused and attempted to fight off the boarders, with only limited success.

Fortunately for the crew, the UNSC Vegas, an ONI Stealth Cruiser, was already on-route to acquire Fireteam Valiant, one of the Spartan teams aboard. When it arrived later that day, it responded to the attack by deploying several Pelicans filled with Spartans to help repel the boarders. After making their way aboard, the SAD teams fought their way through the ship and eventually managed to link up with Valiant and several other Spartans. Through their combined efforts, they liberated the captain, Hendrych Borkowski, and successfully escorted him to the bridge, where he managed to purge Amycus from the ship's systems by activating his fail-safe, destroying his Riemann matrix. With the ship back under human control, weapon systems were brought back online and used to destroy the Forerunner ships, with any remaining Promethean forces being destroyed soon after.

After the operation, Fireteam Valiant was transferred to the Vegas and the Orphellion was directed to a secret ONI shipyard for repairs.