How to Play Dungeon
The Dungeon Players' Guide
Dungeon in the Multiverse: Multiple Worlds
Dungeon is one World within a Multiverse of interconnected Worlds, each with unique challenges, personalities, and laws of physics.
It is possible to move between them. However there are consequences of which to be mindful. You're unable to bring any Items with you when you leave Dungeon. TriadCity and Midgaard have levels, Skills, and many other concepts which Dungeon does not. The Worlds themselves will force you to be mindful of their differences.
One critical distinction is that in different Worlds death has contrasting consequences. In Midgaard, death is inconvenient, but your character is "reincarnated" automatically with loss of exp. In TriadCity, death is permanent. In Dungeon you're forced to start over, but you're not penalized, and you can ">Restore to a previous ">Save point. The laws of physics of the World you occupy at the moment of death are the ones which apply.
Still. Explore! Just always be mindful of the consequences of journeys through the portals.