The Invisible Fortress — Jean Van Hamme

Still travelling with Kris of Valnor, Thorgal runs afoul of a local tribe. When a mysterious old woman offers him a chance to escape the hostile villagers, he accepts. But there's more to the bargain: She says that if he can make his way into the Invisible Fortress, he'll be able to erase his name from the Stone of the Gods, cancelling his destiny -- and finally have a chance at a normal life.