The Ancient Stone Circle is a dangerous location in the western area of the map. The requirements to enter the Stone Circle are non-trivial, which means that generally it is only attempted by quite experienced PCs. There is little reason to enter the Stone Circle unless attempting an Ultra ending or the Ordinary chaos god ending.
In order to access the Stone Circle, the player must meet several requirements: first and simplest, a climbing set is required to access the northwestern region. Secondly, the player must satisfy the Demented Ratling by feeding him six artifacts. The Demented Ratling will then reveal that the Stone Circle can only be accessed during Darknight.
Darknight occurs every 30th day (press Ctrl-E). On the appropriate day, the player must wait until just before midnight (from 23:00 to 0:00) and press '>' to enter the Circle.
|W||Keriax||Multi headed chaos dragon, who holds the Crown of Chaos.|
|h||Chaos Knight||Minion monster.|
|j||Writhing Mass of Primal Chaos||Minion monster.|
|0||Corrupting Pool||Corrupts in addition to usual pool effects.|
Once within, the player will be in a wilderness area with the Temple itself in the center of the map. Access to the temple is on the left side, guarded by two Chaos knights, and two Annihilators. Inside the main room are several Writhing masses of primal chaos, Keriax, the multi-headed chaos dragon, and a pool. The pool is unique in that, in addition to providing the usual pool effects, it also corrupts the PC quite substantially.
The objective in the Stone Circle is to kill Keriax and retrieve the Crown of Chaos that he carries. Keriax is one of the most difficult opponents in the game, with powerful poisonous melee attacks, a difficult to resist confusion spell, and elemental breath attacks that corrupt the PC. He also regenerates his wounds. Standing in a direct line with him is strongly not recommended, but may be necessary to hit him with spells of your own or a wand of paralyzation, and it is strongly advised that some sort of disruption effect, such as confusion or blindness, be applied to him, as this makes standing in a direct line safe. Note that lightning chaos breath attacks can bounce off the walls, so extra attention should be paid to avoid being hit multiple times per one attack. If you do need to risk getting hit with a bolt, be at least double resistant, if not immune, to fire, acid, lightning, and ice.
Note that the temple inside has dungeon floor so it is possible to use webs there, whereas they do not work outside of the temple.