Arkheon Threshold

The Arkheon Threshold was a chronic schism that existed on the planet Arkheon.

Being the center of a small tear in time led to the world being known as the Planet of Ghosts as the time rift created spectral visions. It was a rumour in the distant future during a war between Humanity and the Dalek race and had been believed to had been destroyed forty years ago.

Whilst the world itself was destroyed, the Threshold itself remained and was an objective of the Dalek Empire who sought to locate it from the planet Hurala. This was because the tide of the war was turning against them and meant that they were losing the conflict which they sought to rectify by altering time itself.

The Doctor, after speaking to a Dalek captive, came to the conclusion that the Daleks sought to find the Arkheon Threshold and use it to control Time and Space whereupon they would use their new found power to wipe out Humans from history.

After journeying to the planet Arkheon, the Doctor and his compatriots were captured by the Daleks who had used the information to lay a trap for them. The Dalek Inquisitor General was responsible for a massive mining operation on Arkheon in order for his race to become masters of time by using the Threshold to enter the Time Vortex by using a five storey high massive Chronon collidor to break upon the chronic schism. Despite their efforts, the Daleks were defeated and the Threshold was permanently sealed by the Doctor. (NSA: Prisoner of the Daleks)