Do you remember the time you go in tunnels you have seen something like this: a chair surounded by animals skins ... Use the talisman of the West (or try another?) and a little chest appear on the chair.
This is a first thing. On another place (and I think, but not sure, the other dungeon is that dungeon which have all that platform-stones, do you remember? The stone, if you set a step on it you hear a sound and there appears a chest or ....), also in a dungeon under Brocken Valley, there is a statue and I remember it stay between 2 other things, plants or something .. with his arms up ... On that place you must have all 3 talismans and try things out by "Use" each talisman and choose the right order in a "dialog"! Each time you "Use" a talisman, a thunderstruck fells you, but you not die if you try these talismans again and again.
If you do all things right, again a little chest appears! The Talisman of the North, a good one! The other talismans disappears! That's normal! Success!!