Yuan-Ti Malison

You can only move forward (well, downward) in a dungeon, never backwards or sideways.

A player may only have one dungeon in the command zone at a time.

If you somehow venture into the dungeon while a room's ability is on the stack, you will continue on in the dungeon. If you're already in the last room, complete that dungeon and start a new one.

Once you resolve the last room ability of a dungeon, that dungeon is now completed and is removed from the game.

To venture into the dungeon, a player moves their venture marker into the next room of the dungeon they are currently in. If they aren't currently in a dungeon, that player instead chooses a dungeon card from outside the game, puts it into the command zone, and moves their venture marker onto the first room.

Dungeon cards are not part of a player's deck or sideboard. In both constructed and limited formats, players can use any dungeon card when they venture into the dungeon.