Uma is a Character/NPC in The Witcher 3: Wild Hunt.
"When Geralt encountered a misshapen midget at the Bloody Baron's court. he didn't think much of it. Yet when he heard a similarly deformed being had washed up on Skellige's shores in the same boat in which Ciri and her mysterious companion had sailed off shortly prior, he connected the two at once. It was clear this rough-hewn hunk of flesh was the key to finding Cirilla.
Though Yennefer and Vesemir agreed Uma was suffering from a powerful curse, they could not reach a consensus about how to go about lifting it. Sharp words were exchanged before Vesemir stepped in and announced that before Yennefer did anything he would try one of the traditional witcher methods.
All that was left to the others was to wait.
Though Vesemir's method had worked to disenchant the famous Swan of Poviss. it brought no breakthrough here. Vesemir did, however, succeed in confirming that Uma's body was a sort of magic prison in which some other being was trapped.
Yennefer's method did not prognosticate a high chance for Uma's survival - yet was now the only remaining option for lifting the curse.
The ritual succeeded beyond their wildest expectations. The person cursed inside Uma turned out to be none other than Avallac'h, a powerful elven Sage the witcher had met before.
Sadly, there was no communicating with Uma. The gnarled twiglet lived in his own miniature world. Yet Geralt knew Uma was the key to finding Ciri. Even if no pertinent information was forthcoming from the creature's stunted lips, surely further investigation would squeeze some solution out of this riddle."
A cursed being first seen on Skellige. He was won in a game of cards by the Bloody Baron and taken to Crow's Perch where Geralt meets him. Later, Geralt returns to take Uma to Kaer Morhen where he and Yennefer intend to cleanse him of his curse in hopes that he has some information about Ciri's whereabouts. It is speculated that Ciri was looking to remove a powerful curse and this being may be what she was trying to cleanse.