A door acts as a separation between two rooms.
When a character moves onto a closed door tile, they immediately flip over the door tile to the open side, revealing the adjacent room tile.
Immediately place overlay tiles, monsters, and money tokens as indicated in the scenario description for the revealed room.
While closed doors do not hinder character movement at all, they act as a wall for any monsters or character-summoned figures, and figures cannot be forced through a closed door.
Open doors do not hinder any movement and cannot be closed. Door art varies by environment type, but they all function exactly the same.