Suburban


 * "Underground. Dirt, tunnels, pipes, bogs, sewers. Featuring more maze-like elements. It might get dark here the lower you go, and certain creatures might even glow."

Suburban was the planned first region of the game during beta testing. How exactly the map looked is unknown, but based on the descriptions given, it was likely split up into both Outskirts and Subterranean, with some elements of it inspiring the Shaded Citadel as well. Interestingly, devtools still refer to Outskirts as "SU", indicating the Suburban name stuck throughout development.