:-? I've finished the game, except the iron clan quest. I find the locationa of the entrance but I can't find that darn stone for the key.
There are several heartstones around the Bedokaan Village. You need to get the "lost elven hunter" quest in Qintarra to get the village marked on your map. Useful things, heartstones.
If you have done the Heartstone thing, & gotten to the Place of Lost Voices, the next step is the Dwarf archeoligst in the main temple in Caladon.