Virna was a tomb robber.
She had several sons, whom she used in her explorations. She thought the Fifth Doctor killed her sons, and wanted to let Nyssa die as a result. She had been doing this for centuries. Virna wanted to sacrifice Murs and Heff to save herself. She had previously left her daughter Jhanni on the Arrit tomb ship. She was in the Arrit God-King’s tomb on the ship when it exploded. (Tomb Ship)