Fenris

 (also known as the Hellbringer) was an agent of the Order of the Black Sun. (COMIC: 4-D War)

Biography
Fenris travelled back in time to sabotage the initial Gallifreyan time travel experiments at Qqaba. He caused the stasis haloes on Omega's ship to fail, making Omega fall into the black hole Qqaba. Rassilon's intervention, however, dispatched Fenris and the experiment worked. Fenris's discarded belt provided the much-needed technology to use the new energy and could also be used as a form of directional control. (COMIC: Star Death)

Twenty years after the loss of Rassilon, the Time Lords tried to free Fenris from the Zone of No Return and used the parahuman Viridian to find out he was working for the Order of the Black Sun. But before they could learn anything else, they were attacked by members of the Order of the Black Sun, who killed Fenris and some other Time Lords before vanishing. (COMIC: 4-D War)