Koschei (Inferno Earth)

Koschei worked for the Celestial Intervention Agency in a parallel universe.

Biography
Koschei and Ailla became stranded on Earth for several years when Koschei's TARDIS was irreparably damaged in a battle with the Great Intelligence. His TARDIS was ruined and its central console was cannibalized by the British Republic, allowing them a means of travelling between parallel universes. The British Republic killed Ailla and enslaved the badly injured Koschei, imprisoning him and connecting him to their computers to forcibly take information from him. He was tortured to death several times during his interrogation, using up his remaining regenerations. After meeting himself from a parallel universe, he begged for death, to which his counterpart complied. (PDA: The Face of the Enemy)