My Pet Dungeon is a single-player sort of "sandbox mode" in Dungeon Keeper 2. These maps afford you the luxury of building any kind of dungeon you want, within the physical constraints of the terrain, of course. You begin with the ability to build a Lair and a Hatchery, and all of the other rooms become available to you over time (with the exception of level 6, "Masterpiece", in which all rooms and Keeper Spells are available to you from the beginning). The levels are as follows:
- Liberty (lots of good things to exploit, limited mainly by space and the availability of bridges)
- Discovery (many neutral rooms to claim)
- Bottleneck (finite gold supply)
- Recruits (no Portals, only neutral creatures to be claimed)
- Furnace (oddly-shaped islands surrounded by lava)
- Masterpiece (lots of space, no room timer)
- Torment (best resources hard to reach, mostly protected by Traps)
Each level has a particular point total as its goal, and two special tasks that will grant you most of the points you need to reach this goal.
The only enemies you face on these maps are the ones you want to; each map contains a "Hero Toolbox", which contains one of each kind of non-unique hero as well as a lever-bearing device (resembling a slot machine) to increment their level (or to set it from 10 back down to 1). This enables you to pick up any hero of any level to drop into your dungeon. Each map also contains a Hero Gate from which you can launch a single invasion of Heroes of a single level, or trigger a continuous invasion in waves that progress through the levels up to 10. In the lower-right corner of the GUI, where the pieces of the Horny Talisman or the Summon Horny button appear in the campaign, are buttons allowing you to trigger either kind of invasion or zoom to the Hero Toolbox.
Also, in My Pet Dungeon mode (with the exception of Masterpiece), the only spell you start out with is Create Imp; all of the rest must be researched in your Library. Your Library should therefore be bigger than normal, to accommodate nine spell books in addition to any magical items you may find (upgrading existing spells does not take up shelf space, but requires there to be at least one empty space in order to proceed).