The Beast appeared in the episodes Impossible Planet/The Satan Pit(2006)
The Beast said that he had many names, including Satan. He claimed that he remained imprisoned since before the universe.When the Doctor encountered him, the Beast resembled a gargantuan crimson horned figure with a corpse-like face, bound by chains.
The Beast could manifest himself through electronic media, including computer voices and, crudely, through hologram viewers. Its mind could leave its body and possess a single hive mind of the Ood collectively or a single Human individually, though not more than one at one time. He had the power of telepathy and, through a host, telekinesis, manifest fire from his mouth and affect the hosts skin, causing strange markings to appear all over their face and body, and vocal chords, allowing them to speak with different pitches simultaneously.. His hosts could also physically survive in a vacuum indefinitely.
Though the exact circumstances are unknown, it is known that the Disciples of the light confined the Beast to the planet later known as Krop Tor and placed the planet in orbit around the black hole K37 Gem 5 . If he ever tried to escape, the field holding the planet in orbit would stop and the planet would be sucked into the black hole.The Beast claimed to have existed before time, a claim the Doctor found difficult to accept.
The Beast spread his influence throughout the cosmos. He claimed that the devils and demons that appear in various religions were based on him.
The Beast had a son known as Abaddon.
The Beast possessed Toby Zed, a crew member of the Walker Expedition Sanctuary Base.
Through Toby Zed, the Beast's first action was to kill Scooty Manista by breaking one of the windows (the Beast and those he possesses can survive in a total vacuum of air ). The Base's Ood were taken over. Upon the Ood's defeat, the Beast planned to escape by keeping his spirit in Toby's body, leaving his physical body behind. The Doctor deactivated the force holding Krop Tor in orbit (the beasts' body) thus making the planet fall in to the black hole.
The Beast's original body was destroyed when Krop Tor fell into K37 Gem 5 and his spirit is believed to have been destroyed when Toby's body was pulled into K37 Gem 5 after Rose shot the front window in the escape spacecraft so he would be sucked out because Rose took of his seat-belt, although he claimed that he would never be truly destroyed.
Impossible planet/The Satan Pit(2006):The Doctor and Rose land on a planet which is standing up to the pull of black hole, but what is the source of this power? Have Rose and the Doctor gone to far? Will what they witness be too much for them?.....