A disfigured Australian mutant who possesses the power to shape-shift. All he needs to do is look into someone's face, and his molecules can recreate the person's image, voice, and clothing. His body can also mimic inanimate objects as well (e.g. when he had his hands mimic a branding iron; after he got shot with a laser, he could mimic the laser's heat). Not much is known about his past, he has stated that he had a life before the Defiance experimented on him, and that he was an Olympic athlete, which is shown when he is able to evenly fight Aaron. He impersonated Aaron and kidnapped T. Abner Hall, but Aaron managed to rescue him. U is the third mutant to be captured by Aaron. He is captured in the episode "Pack-Man". He escapes in the series finale and helps Damaged and Elias Powers with their plans. U is captured in the series finale, but disguised as Elias Powers, while the real Elias Powers goes into the "Uriah Chamber".
- Although U can shapeshift into anyone and anything, it's possible he can't mimic everything about them, as in Face-Off, he couldn't mimic the heat from Aaron's gauntlet, allowing S T.A.N to realize that it wasn't Aaron, and in Mutant Rain part 2, U shapeshifted into Elias and was apprehended by Emma, but when she was hitting him, U was showing signs of feeling pain, which is something Elias can't do.