Dimensional Tear
From The Monoverse: A Non-Linear Sci-Fi Epic
A dimensional tear is big enough for a human to crawl in or step through. A tear appears because a leak has been worsened, or because the energies of a dimension had a "crash" between each other.
A tear is usually permanent unless repaired. It is hard to find a Tear, however at the right angle you can see a slight sparkle coming from it if looking at the right time. A tear does not typically pose a threat, but potentially it can conjoin the energies of two dimensions and push them together, eventually occupying the same space.
It is theorized a "Dimensional Crash" has happened more than once and may actually have decreased the amount of potential dimensions to a manageable amount.
