Dungeon Overlord consists of two types of dungeons, the starter dungeon and the expansion dungeon. All dungeons consists of a 24x24 grid of Tiles displayed isometrically. the starter dungeon will only have a single entrance on the upper-right ("north") side, with a hallway connecting that entrance to the Vault. Expansion dungeons can have up to four entrances on any of the four sides. The exact number and placement of the entrances a dungeon has can be seen in the internal mountain view accessed by the Overworld map.
All dungeons begin with a Vault in the center, enough hallway tiles to connect each entrance to the vault, and various resources scattered around randomly. Players may build dungeons in any fashion they wish, so long as they follow the following rules:
- Hallway tiles can be placed anywhere in a dungeon and do not need to connect to an entrance. Unconnected hallway tiles cannot be built into Rooms.
- All entrances must connect to the Vault either directly or indirectly. The connecting tiles may be Hallway, Resource, or Room
- Rooms must have either a direct or indirect connection to both an entrance and the Vault to be considered active.
- Players may not exceed the number of available tiles to them when building. See the Technology Tree for ways to increase the number of available tiles.
- Players must have the required amount of gold to purchase a specific room tile. Note: Hallway tiles do not cost gold, however they do count against the total of available tiles.
- When selling tiles:
- Players may sell any Room tiles for considerably less gold than the original cost leaving behind a Hallway tile.
- Hallway tiles may be "sold" adding to the number of available tiles. A Hallway tile cannot be removed if it would cause a violation of any of the above rules.
- Vault tiles can never be sold.
At level 1 a player may only occupy their starter dungeon. As a player gains levels, they may acquire additional dungeons. Their second dungeon is acquired when they accumulate enough Experience points to reach level 10, the third at level 20, and so on. Players can Survey other dungeons in their mountain and surrounding mountains using the Overworld map to to determine which Resources are available in each location. Once the player finds a location with their desired resources, they can send a goblin to establish ownership of the dungeon. If the player later decides they no longer wish to occupy the dungeon, they can always Abandon it. Abandoning a dungeon destroys all of the rooms, upgrades, and any furniture or resources left behind.