Arkheon

The planet Arkheon was, according to the Tenth Doctor, a "Lovely place". It was the site of a time rift known as the "Arkheon Threshold", which often caused temporal "ghosts" to appear, a phenomenon for which the planet became infamous for.

History
During the First Dalek Incursion, Arkheon was hit by a "Planet-splitter" missile. The missile strike caused the destruction of one half of the planet, exposing the core. The fallout killed most of the inhabitants, with the survivors eventually mutating into mindless savage beasts.

Forty years afterward, it was discovered by the Doctor and the crew of the Wayfarer that the Daleks had turned the area around the core into a slave labor mine in an attempt to locate the Threshold and use it to become masters of Time. The Dalek force behind the operation were later destroyed by the Doctor. Earth Command then sent in forces that destroyed the remaining Daleks and freed the prisoners, and the Doctor sealed the Threshold, ensuring the Daleks could not exploit it. (NSA: Prisoner of the Daleks)

Arkheon