The Void

Known Info.
The Void is a Vortex/Dimension that is mentioned in Army of Ghosts and Doomsday it is also the path between paralell dimensions (parallel earth)

Void Travel
Creatures and people can travel through the void with void ships ]]

In Army of Ghosts and Doomsday The Cult of Skaro travel to earth from Parallel Skaro (?) and that opened up the void again so the Cybermen came through (unknown to all travelers at the time).

The void is Like