Nether Gate of Tersimmon

The  was a device that could siphon the dark energies out of N-space and into an uninhabited universe to prevent them from corrupting all of life. These were operated by the Apocalypse monks of the Andurax which required four gemstones, the Hazandra, the Arquess, the Alcyone and the Sanguinare to open this rift safely. The Doctor was able to obtain them all with the help of Grant Gordon, Lucy Fletcher and Jennifer Fletcher. (COMIC: Ghost Stories)