The demon lair is a pocket of infolded space that powerful demons are able to creat and influence.
Therefore it can be shaped to whatever their twisted mind can entertain and sustain, be it a dungeon, a dreamspace, or whatever. Typically, this takes the form of series of rooms, maze or dungeon. Most of the rooms serve a function for the demon or its inhabitants, from worhsip of its evilness, training, lodging, torture, experiments, ritual, farming, factories, forges, mines, or a twisted mind-trip of confusion and chaos.
The demon lair can be inhabited by:
- minions of the demon's creation
- minor fabricated creatures
- corrupted creatures
- possessed creatures
- children of the possessed
- traps
- automatons and golems
- minions invited or enslaved
- hellspawns
- mind-controlled critters
- magical beings with cruel intent
- evil spirits
- lesser demons
Destroying the main demon will collapse the lair and send some creatures back to where they came from. The rest are all out into the opening of the demon lair, whether they be free from corruption, or angered and ready to wreak havoc. Not a great idea to rush to the boss before killing most of the baddies lest you terrorize the locals with a demon plague. The gates can also be sealed so that the threat can be dealt with at a more reasonable pace. Using
rune magic, a character with the correct knowledge can cast a spell upon the gate that prevent any monsters at the same level or lower from leaving.