UNC: Missing Marines

UNC: Missing Marines is obtained by speaking to Rear Admiral Kahoku in the Citadel Tower after Commander Shepard has been granted Spectre status. You need to travel to the Sparta system in the Artemis Tau cluster. Once you arrive in orbit over Edolus, you detect a distress call.

On the planet, you find the missing marines; slain by a Thresher Maw. You now need to return to Rear Admiral Kahoku in the Citadel Tower.