After defeating Cicatrix the undead centaur, you loop around the magma, like Tom said, and when you climb the hill, you find a displacer. This displacer takes you back to the half giant clan so you can trade with them. But you need to use the displacer to go back to where you were (in the Mountain of the Dead), so you can continue to climb the hill, past the displacer. This is how you continue on.
[color="Gray"]"They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." Ben Franklin [/color]