Callisto is leader of the Morlocks.
She captured Cyclops intending to make him her mate. The other X-Men arrived to save him and did battle with the Morlocks. Storm fought Callisto one on one for leadership of the Morlocks, and won. She did let Callisto rule in her absence.
She grew upset that her leader Storm rarely went down to the Morlock tunnels. When Leech was sick Callisto watched over her. On Christmas Eve Storm arrived to help and Callisto voiced her disapproval. After Leech was healed Storm gave up her position and handed it back to Callisto. As her first act as leader she invited the X-Men to join in their Christmas dinner.
Callisto was voiced by Susan Roman.
First version of the character outside the comics.
In the Comics
It was Angel, not Cyclops, that Callisto captured to make her mate.