Mula was the granddaughter of Balaton and the sister of Pralix. Mula was openly frustrated with her grandfather's complacent attitude, and she was bitter over how her father, like Pralix, showed Mentiad characteristics and was taken out into the street and shot by the Captain's guards.
She aided the Fourth Doctor by taking K9 to the Mentiads, and subsequently joined the Mentiads and Romana in the final stand against the Captain. (TV: The Pirate Planet)