Jillonga was a Trimestrian. She was the wife of the Trimestrian Warlord Bloodgrudge and the mother of Yanta and Slopp.
Seeking revenge on the Doctor for her husband's death, Jillonga took her children out of school on a sixty-year journey to 21st century Earth so they could see her revenge, and posed as a human called "Jill Ongar". She disguised her spaceship as a house in London and emailed Mickey Smith that she had information about the Doctor and the organisation UNIT. After Mickey arrived, she intended to send her ship on a sixty-year trip back home, questioning Mickey all the way about the Doctor, whom Jill suspected Mickey was more familiar with than he let on. Mickey tricked Jillonga's children into playing a game where he waited outside the airlock until he knocked. With the ship unable to change course on its trip home, the ship launched, and Mickey was left behind on Earth. (PROSE: Taking Mickey)