Merry Gejelh

 was a Queen of Years on Akhaten. She was chosen as Queen and was taken as a baby, after the last Queen of Years died. She was afraid of singing to the Old God and ran away. As a result of this, she ran into Clara Oswald who talked her into singing to the God. Clara later regretted this when Merry was kidnapped to be feasted upon by the creature.

Clara and the Eleventh Doctor went to rescue her and fought against the Vigil in order to protect her. After Clara managed to get her to safety, Merry was determined to help the Doctor defeat the Old God, which was actually a parasitic planet. She sang defiantly to the parasite and the other guests followed her example. With the Old God growing weaker from their defiance, and the sheer amount of memories the Doctor possessed, Clara went back to help the Doctor finish off the creature once and for all. (TV: The Rings of Akhaten)

Personality
Although she was very knowledgeable about songs and history, Merry was still very young and was frightened of getting the song wrong when she sang it to the Old God. She ran away and hid out of fear of making a mistake and enraging the Old God. When she met Clara, Merry was initially wary of her, but quickly grew to trust her and even hugged her at one point. She looked to Clara for support before she began singing. When Merry was kidnapped by the Old God, she didn't understand why, having not been prepared for that, and thought she had gotten her song wrong. When Clara and the Doctor arrived to rescue her, Merry, still panicking over her perceived mistake, yelled at Clara and then used her telekinetic powers to pin her against the Mummy's glass prison. The Doctor managed to calm her down and she released Clara soon afterwards.

Despite the fact that she was a terrified and confused little girl, Merry did have a brave side and was determined to help the Doctor defeat the Old God, singing to it in a display of defiance. She was also selfless and nearly sacrificed herself to the Old God, hoping to protect her people by doing so.

Abilities
Merry's species was never mentioned, but she had some form of telekinetic power which she used to restrain Clara when Clara was trying to get her away from the Mummy. She could control these abilities simply by thinking and freed Clara soon afterwards.