Demon

An unnamed species of Demon existed before the universe who were the enemies of the Disciples of the Light.

Appearance
Demons are immensely tall humanoids with skin colours ranging from blood-red to pale green, and horns ranging from long and curved to short and straight. (DW: The Satan Pit, TW: End of Days)

History
Before this universe, the Demons fought a war against the Disciples of the Light. When they came into this universe, they fought in Mutter's Spiral, however the Demons ended up outnumbered and imprisoned by the Disciples and became imprisoned in various places including simple prisons under time rifts (such as where Abaddon was buried, under the Cardiff rift) and in complex traps around black holes (such as where The Beast was buried, in Krop Tor orbiting K37J5). The Discples then seemed to disappear from existence. (DW: The Impossible Planet / The Satan Pit, TW: End of Days)

Doctor Who

 * The Impossible Planet / The Satan Pit

Torchwood

 * End of Days