You can build a stairs dungeon with only a rug in the middle or just nothing if you like. You can also have 2 monsters in that room. Unfortunately none of the monsters will give you any combat XP. As far as I know none of the monsters can use magic or ranged attacks but the Steel Dragon can attack you from a distance with his fire breath (what deals a lot of damage). The monsters in the treasure room can't leave the room. It isn't ought you to build any doors in your dungeon if you wish so.
Hi this is my houseplan. The ground floor: The first floor: And my dungeon but I don't know yet how I'll make it, but if anyone has an idea, you may say it.