Circle of Transcendence

The Circle of Transcendence, alternatively coined the Red Carnivorous Maw by Cleopatra Hunsicker, was built by Anubis with the help of his key by Horus' request.

Its purpose was to allow all surviving Osirans to escape to a higher, four-dimensional universe. By Horus' command, Anubis was left as the Circle's guardian until all Osiran technology is purged from the universe. The millennia that the purge required caused a degradation in the polar quantum articulations. If Anubis used the Circle to finally ascend himself, the universe would have been destroyed. The Tenth Doctor and Dorothy Bell managed to persuade Anubis to wait until the Doctor helped him to fix the Circle. (COMIC: Sins of the Father)

Anubis was possessed by the fragments of Sutekh and was made to align the Shining Horizon with the Circle so that Sutekh, along with other enemies of the Doctor that had been trapped, could be freed. Sutekh then prevented himself from being pulled back towards the Circle by throwing the Destroyer into it and blocking the flow of energy. (COMIC: Old Girl)

The Tenth Doctor would later recall saving a planet from the "Red Carnivorous Maw" to Ood Sigma during a visit to the Ood Sphere. (TV: The End of Time)