Light filters down from a hole in the ceiling to illuminate a massive cavern. The hundreds of purple crystals studding the cave's floors and walls glint and sparkle in the dim light.
These magical gems intensify the power of spells cast in this area. As a result, the various factions that live in this underground world frequently fight for control of the Crystal Cavern.
A small fortress stands in the center of the cavern. It was stone shaped out of the cavern itself many years ago, and consists of a two towers connected by an 8-foot-tall square wall, itself surrounded by a 4-foot wall, large enough to fit several dozen people if all they want to do is defend it. Half a dozen semi-permanent structures crowd around it to serve as kitchen and storage.
Enemies within the cavern are not the only threat. In times past, multiple enemy forces dug trenches underneath the fortress. Some of these have collapsed; in some cases the fortress's defenders closed them off and used them as storage. It's said that several dangerous artifacts remain lost in these tunnels.
There are enemies above, too. A tribe of vulture-folk occasionally climb out of holes in the ceiling and swoop down on unsuspecting victims. (Use stats for aarakocra.)
- The PCs need an artifact that lies underneath the fortress.
- The PCs have to get supplies to an embattled faction within the fortress.
- The PCs are part of a war band sent to overtake the fortress