Order of the Black Sun

The Order of the Black Sun was a group that waged the First Great Time War against the Time Lords, the first time war the latter had ever fought.

Membership
Several different species, some humanoid, others only vaguely humanoid, made up the Order. They wore capes and black unitards with a logo on them. (COMIC: 4-D War, Black Sun Rising) They used hand-held black orbs as the focus for blasts of power. (COMIC: 4-D War)

They were represented by an Elder, as well as representatives for different space sectors. (COMIC: Black Sun Rising)

Origins
One account noted that a "Cult of the Black Sun" was among the many secret societies which Faction Paradox created among the "lesser species", telling them "all the nastiest secrets of the Time Lords". (PROSE: Interference - Book One) Indeed, a mysterious black sun which functioned as a corrupt antithesis of the Time Lords' Eye of Harmony was a prominent omen of the post-War universe that would follow from the fall of Gallifrey, (PROSE: The Adventuress of Henrietta Street) and had been a cause of concern and speculation among the Time Lords well before the War in Heaven that would bring it about. (PROSE: The Gallifrey Chronicles)

Time War
30 years after the disappearance of the Time Lord Omega, they sent ambassadors to trade with Gallifreyans and Sontarans. Their Elder was killed because of a Sontaran plot, whose fault fell on the Gallifreyan delegation. The diplomatic incident triggered a conflict against the Time Lords. (COMIC: Black Sun Rising)

About 30000 years later, they had developed a time travel technology, the time-jumper, with which they sent back an agent to prevent the birth of the Time Lord civilisation itself, but they failed, inadvertently helping Rassilon to develop time travel. (COMIC: Star Death)

20 years after the disappearance of Omega, a group of them showed up inside the Question Hall on Gallifrey to stop the telepathic parahuman Viridian from unearthing information from Fenris the Destroyer's ruined mind. 11 people who were inside the Hall were killed, including Viridian and Fenris. (COMIC: 4-D War)

Aftermath
Long after the time war, a member of the Order of the Black Sun would serve as a High Evolutionary. (COMIC: The Final Chapter)

Behind the scenes

 * Alan Moore mentioned that he intended the Order as a reference/tribute to DC Comics', identifying them as originating from Earth-5's reality (as opposed to DC Comics multiverse, whose main realities were Earth-1 and 2).