Abaddon
Abaddon was a Demon and the son of the Beast, who was imprisoned beneath the Cardiff rift on Earth. However, the Ood named stated that Abaddon was a name for the Beast itself. (DW: The Satan Pit)
- Abaddon was probably imprisioned by The Disciples of the Light, who imprisoned his father on Krop Tor.
A 1827, archaelogical expedition excavating the ruins of Babylon experienced found a stone tablet depicting a Demon standing above a city. (WEB: torchwood.org.uk)
Bilis Manger, considering himself Abbadon's servant, set in motion of series of events designed to manipulate the Torchwood 3 into using the Rift manipulator to open the rift and release Abaddon. (TW: End of Days)
- Abaddon seems to share none of the intelligence of his father and was not shown to speak or plan. There is still the possibility that he was the one who created the plot, rather than Bilis Manger himself.
The shadow of Abaddon killed any person who it fell upon and fed upon their life energy. Only the undying Jack Harkness stood in his way. He was eventually killed by Abaddon, the Demon dying in the process due to the excess life. However, Jack came back to life. (TW: End of Days)