The area where you can descend into the Kuo-toa area, on the right side of that pit - and you have to look closely, there is a rounded alcove with small mushrooms in a ring. If you look at the active one going in and out of the hags lair its the same thing. If you walk onto it your character says something like "huh, an inactive fairy ring, I wonder why it isn't working like the others". Ran around the hags lair trying to see if there is anything there that would indicate a power source, through tons of sylvan stones on it, drank all the hags potions, equipped everything she had had, dropped it all in the ring, cut myself to coat it in blood, blessed myself, cast light on items, sacred flamed myself inside it, used a bunch of crystal, used sussur blossoms, bunch of stuff. Cant think of what else would activate something like that.
