Mist

Mist is a playable character from Fire Emblem: Path of Radiance and Fire Emblem: Radiant Dawn. She is Ike's younger sister, and the daughter of Greil and Elena. She fights with the Greil Mercenaries out of a fear of being separated from her brother, using healing magic taught to her by Rhys. When the Medallion reaches its critical state, Mist is the only beorc to be affected by its call, and collapses in a similar manner to the Herons.

(Source: Fire Emblem Wiki)