U-Mos was the last of the Luminoth species who appeared in the Gamecube video game Metroid Prime 2: Echoes. He was a friend to Samus Aran, though his species nearly became extinct during the attack of the Ing. Before Samus Aran appeared, he ordered that the rest of his species go into hibernation. He asked Samus to go and save the light demension of Aether, the planet that was at the time being attacked.
Once Samus saved the world, the Luminoth would be able to awake from their slumber, allowing the intelligent species to once again flurish the planet.
During the in-game events, U-Mos was 200 years old, though apparently that is young for the species, who have been recored to live up to 1,000 years.