Queen Belldonia was the wife of King Paladin the Great of Peladon and the grandmother of King Pelleas.
She disapproved of her grandson's arranged marriage to the Earth royal, Princess Pandora. Belldonia and Grok were two of a handful of people that knew of the Aggedor that was kept secret beneath the citadel of Peladon. They often went on hunts with this Aggedor. On one hunt in the forest in the 41st century, the Aggedor began circling the Fifth Doctor and Erimem. However, the Doctor tamed her with Erimem's signet ring. Grok returned the Aggedor to the dungeons while Belldonia took the Doctor and Erimem to the citadel.
When the Aggedor knocked down the doorway to Sekhmet's tomb, she started having labour pains. Belldonia looked after the Aggedor as she gave birth. (AUDIO: The Bride of Peladon)