History
Luna was a young mutant from the Age of X-Man who telepathically froze a whole community in place during a psychic seizure. She was rescued by Nate Grey, who helped her to calm her powers and then took her to the Summers Institute so that she could train her mind against future seizures.
It is unknown if there is a version of Luna outside of the Age of X-Man. If there isn’t she would have perished when the pocket dimension was destroyed.
Powers
Luna is an untrained telepath, powerful enough to paralyze a whole community of fellow mutants.