I was thinking about stone circles the other day, as you do. And, in particular, I was thinking about finding a role for them in Terafa. And while thinking on this, my thoughts proceeded to stay in an entirely different direction, as they are sometimes wont to do.
Initially, I was considering whether a stone circle could just perform much the same role as they did in the real world - essentially as a very ornate clock. But that seemed rather bland - what about casting them instead as a count down to some event. That struck me as being better. But...
Then it occurred to me that actually the stone circles in the real world were never just a clock. They also served as a centre for religious worship, as a focal point for communities, as a market place... oh, and there's at least some evidence of their being used for ritual slaughter (or, perhaps, just a great big barbeque).
Of course, it's also worth considering that many of these uses were not the ones the original builders intended - the site would have been taken by others, who modified it for their own use and claimed it as their own (that is, cultural appropriation).
All of which got me to thinking that perhaps a stone circle should be a fairly detailed adventure site, with no fewer than four layers of uses about the place, two of them known about and two of them being secrets to be learned by the heroes:
Layer One: My first layer of usage would be that of the current inhabitants of the place, who use the stone circle as a community focus point - they have annual harvest festivals within the great ring.
Layer Two: The previous owners of the site were a tribe of bugbears who were driven out about a century ago. They used the site for burials, with many of their champions buried in barrows around the area. Much treasure can be found here, but much danger also, for the spirits of those champions linger here still. Of course, this usage is known to the locals, as their history records the presence of the bugbears, and the burial mounds are likewise known.
Layer Three (secret): Some time prior to the bugbears arriving and claiming the site, the stone circle was home to a cult of demon-worshippers. Their lord was a dark and fell creature who demanded ritual sacrifices from his followers in the depths of the winter solstice. The stones are thus saturated with the blood of those sacrifices, and indeed tainted by the spiritual energies thus released.
Layer Four (secret): Finally, we come to the original purpose of the stone circle. In the distant past, a dark and terrible faerie lord was imprisoned here by lizardfolk in the area. These lizardfolk were servants, and some say worshippers, of an ancient black dragon, who fought the faerie lord to a standstill while his followers enacted his capture. However, the ritual was imperfect, and so the circle counts down to the release of this captured lord - every year the shadows of the stones grows just a little shorter, and when the shadows are gone entirely, the imprisoned lord will once again be freed. (Of course, the truth of this is known only to the draconic spawn of the ancient black dragon... and she's not for sharing.)
The notion here, then, would be that the PCs initially arrive for the harvest festival on the site, and gradually become embroiled in strange goings on surrounding the location. Naturally, they may find themselves enticed by the prospect of fortune and glory in the burial mounds, but as the psychic energies around the place swell, and as the release of the faerie lord becomes nearer, they would have more to deal with.
Right now, it's only a half-formed idea... but there's some promise there, I think.
