The Fortress

The Fortress was a building placed in the city of Arcopolis by one of the factions in an intergalactic war. It housed a weapon which was capable of not only destroying its target, but also destroyed all evidence that the target existed, as well as killing anyone who knew about the target, meaning that anything destroyed by the weapon would effectively vanish. However, people destroyed by the weapon returned as ghost-like beings that pulled anything they touched out of reality. The weapon was cylindrical and was activated by touch. It was later evealed that the weapon did not function properly.

A group of Eyeless landed on the planet and attempted to take the weapon. The Tenth Doctor defeated them and destroyed the weapon.