The mushrooms on the wall near the Kuo-toa(sp) village (outside of it, before you take the cliff down). It's located at X: 78, Y: -274, which is about midway between the Underdark Fort and the Ruined tower....
Has anyone been able to figure out a way up them yet to get on top of the ledge? I know if you do something wrong, the pathway up top also closes. There's like two portal looking things up there, trying to figure out what this is all about. Any help would be appreciated =)