The interdimensional "buffer zone" between universes.
The universe is a big place, but not nearly as big as the multiverse. By some accounts, there are as many Earths as there are atoms in the planet Earth. The Blur is an interdimensional sub-reality that forms the barriers to these alternate universes.
As perceived by humans, the Blur is a swirling maelstrom of darkness and color. The Blur is not a pleasant place, and not safe for the average traveler. Every human incursion into the Blur has repercussions and echoes, so traveling there without a specially designed shiftship is not a good idea. One such shiftship is the Corvette.