Liam O'erspace was a native of Algol at some point after the 20th century. He looked human except for his eyes, which glowed like fire. He travelled through time to 1980s Putney, where he supported himself by placing bets on events whose outcomes he knew, bringing him to the Seventh Doctor's attention.
Wanting to get home and requiring psychic energy to power his signalling device, the members of Ace's gang offered to sacrifice Ace to him. The Doctor stopped the proceedings, then convinced Liam to leave Earth with Arishma, who had been sent after him. (PROSE: Teenage Kicks)