Kingdom beneath the sand, paperback/jean van hamme

Its been two years now since Thorgal and his family left the north to look for some hypothetical country where men might live in peace and harmony.

They are sailing along a deserted and inhospitable stretch of land when Aaricia and the children convince Thorgal that enough is enough.

But before they have a chance to turn around, they come across two strange characters who seem fascinated with Thorgal, and that night their boat is mysteriously torched.