Leah

The Ancient Spirits of Evil bring the Mirror Wraith to Mumm-Ra, and he disguises it as a child's toy. Mumm-Ra then intercepts a thunderian escape pod which carries in it a little girl. He gives the toy to the child (Leah), and leaves. She is rescued by the Thundercats, and goes into New Cat's Lair with the doll. The doll turns into the Mirror Wraith when left alone, and begins to destroy Cat's Lair, and the Thundercats have no clue where the evil Mirror Wraith came from.