Calisto is the Artemis main servant. She is a leader of Satellites.
In this movie, she frees Toma from his prison to kill Seiya, but she appears only in the one-shot manga prologue of this movie.
Athena Hunt in Next Dimension
Artemis forgives Athena sinner in Next Dimension and decides don't kill her. But, fearing Athena's threat to Artemis, Calisto sends Lascoumoune to kill Athena, and after, free Tohma and orders him to kill Seiya, like the movie.