So, I like to write headcanon for games I play. It helps with immersion. In Terraria, I figure it's like the Cardiff Rift in Doctor Who / Torchwood: you're dimension hopping in a region where the wall between dimensions is very thin, so it's easy to shift from one dimension to another. This explains the weird mix of tech levels, the ability to go to any world with any character, the underground cabins and pots full of cash & potions, etc. Any thoughts?