It looks good. Can you flare the underwhere out a little bit around the keister of Gawd, possibly connect the island to the southeast to the mainland of keister island? I kinda want more underwhere to play with (don’t tell my wife).
The Underthere with major tunnels marked. Yellow circles represent transition points to the surface, blue circles are transition points to the Nether Regions. Green lines are “Slog Class” tunnels – capable of transitioning a Slog Schooner (Whopping big tunnels!). Purple tunnels are “Caravan Class” tunnels capable of being transitioned by mounted riders and decent sized wagons / conveyances. Pink lines depict “Foot Class” trails that can only be navigated on foot .