Universe 6 is a universe that was first mentioned during Epic Universe: Next Generations. In order to get there, you must surpass Deity Level 20. There is no other info known about it, other than that Viaton was sent to Universe 6, and it presumably houses a lot of incredibly powerful beings. It is not connected to Universes 1-5. The Universe is then brought back into the story when the Next-Gen heroes go to confront Viaton.