K37 Gem 5 and Krop Tor were set up by the Disciples of the Light to imprison the Beast. The Beast was trapped within Krop Tor and a power source was implanted to keep the planet from falling into K37 Gem 5. If the Beast tried to escape, the power source would fail and the planet would be dragged into the black hole. (TV: The Satan Pit) As the Doctor, Rose and the crew of the Walker Expedition watched, the Scarlet System, home system of the Pallushi fell into K37 Gem 5's gravity field.