The Undermere (`undermere`, new)

Layout: the mouth and ladder; the first cavern under the reflected roof; the den (market, pit, board); a tunnel north to the diggings under Corran's warp; a crack up the gorge to the Hour Stair's window.
Spawns: Spawn_mouth. Exits: Exit_mouth (overworld), Exit_corran, Exit_climb.
Triggers: Event_ladder, Event_market, Event_ring, Event_board, Event_atonement, Event_climb_start, Event_diggings.