Dæmos

Dæmos was a planet roughly sixty thousand light years from Earth, on the far side of the Mutter's Spiral. The Dæmons were from this planet. (TV: The Dæmons) Like a million other worlds "right across the universe", Dæmos had "the representation of the horned beast" in its myths and legends. The Beast claimed to be this "devil", along with all of the others in every religion which had such a figure. (TV: The Satan Pit)

Damos was off limits to all Time Lords, including Celestial Intervention Agency operatives, due to the high potential risk of Dæmons attaining time travel. The CIA worried that the Master might involve the Dæmons in his plans. (PROSE: CIA File Extracts)

During the Dæmons' "private Götterdämmerung", many of them died in battle form and their gigantic remains remained on Dæmos. Long after the planet came to be "infested" by the lesser races, Faction Paradox of the War in Heaven unearthed Dæmon skeletons from the planet and converted them into warships, (PROSE: Interference - Book Two) which were seen by Mother and Father as "skeletons pulled from the influence of the Infernal Sphere". (PROSE: The Story So Far...)

Behind the scenes

 * Philip Purser-Hallard's short story T.memeticus: A Morphology, from the Faction Paradox anthology The Book of the Enemy, features a Daemon-like race that lives in the the Infernal Sphere, a Dyson sphere built around a black hole. The anthology's editor, Simon Bucher-Jones, later used that version of the Daemons in the short story Doctor Who and the Exile from Hell in Obverse Books' charity anthology A Second Target for Tommy. That story implied that Daemos and the Infernal Sphere were one and the same.