Dimensional rift
From Tardis Wiki, the free Doctor Who reference
A dimensional rift was an opening between dimensions.
It 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)
