Chunks of time vortex that can all connect up nice and easily, we have it so that it spawns in a straight line, but then randomise the pieces. It is a dimension you can access by entering manual flight while in vortex flight. The controls of the TARDIS act as if you're wearing an elytra but with increased momentum. Touching the side of the vortex walls (block based to prevent hyper amounts of lag and so the pieces can match up) forces a materialisation, if you do it before the time it would've taken to landed normally, you land closer to the location than if you were to have crashed at that exact instant. If it's in the randomised flight mode, it'll re-randomise.