Players have the option to Abandon any expansion Dungeon they Occupy. Starter Dungeons are not able to be Abandoned. Anything in the Dungeon, when Abandoned, will be lost forever. Because of this, many players will Downgrade Rooms, Transfer Creatures, Ship Furniture and other Resources, as well as sell Tiles before Abandoning.
To Abandon an Expansion Dungeon, players can choose the Dungeon panel from the Overworld. They may select the Dungeon they wish to Abandon. The Abandon button is on the right side of the panel. After choosing to Abandon, players will be prompted to confirm the action. Once the Dungeon is Abandon, players may Occupy another Dungeon to fill that slot.