The Apocalypse Element was the name the Daleks gave to particles that were an entropic power present within crystals which were capable of channelling mental energy that behaved contrary to the laws of physics.
The Monan Host made use of the Apocalypse Element in their temporal technology as it was capable of being manipulated telekinetically in a zero gravity environment. The Dalek Empire harvested the Apocalypse Element from Etra Prime in the Seriphia Galaxy, which they detonated, destroying everything within it, and allowing the Daleks to reshape it as their new power base. (AUDIO: The Apocalypse Element)