Dimensional rift

A dimensional rift was an opening between dimensions. Essentially a wormhole, a dimensional rift was traversable, in that matter (including beings) could cross from one end to the other. Project Infinity was developed to open a dimensional rift. It was through such a rift on Lopra Minor that the Daleks from an alternate universe passed through. (BFDE: "Death to the Daleks!", Project Infinity)