The Fold
From Threesong
The rift between Limbo and the Oubliettes isn't the worst obstacle in a trip around the wheel; At the boundary between Bytopia's two layers, and in a radius straight through the Outlands and the center of Tradegate is a little wrinkle in spacetime which causes anything which passes through it to turn inside-out. This is problematic for commerce and beneficial for avoiding visiting cousins, but Astral-based teleportation crosses it fine, as does light and sound. As such, train routes from the Five Remaining Heavens and Arcadia to Elysium and the Beastlands take the long way around, south of the Oubliettes, and through the Clammy Desert.
