Historical Rules · 29 April 2022
Rule 309.5b
Official source text from the 29 April 2022 Rules release
If a player ventures into the dungeon while they own a dungeon card in the command zone and their venture marker is on that dungeon card’s bottommost room, they remove that dungeon card from the game. They then choose a dungeon card they own from outside the game and put it into the command zone. They put their venture marker on the topmost room.