@vikingmaker Another possibility other than mythology is try to be historical. The Viking invasions of Northwestern Europe are gameable. Don't try to be a 4X game, TripleA is not a good engine for that. Conceive it in TripleA terms as a conflict between Denmark, Norway, Mercia, Wessex & the Frankish Empire. It is nicely asymmetric conflict which reached a definite conclusion.
Another historical possibility is the conquests of King Knut. Everyone is Christian but the Scandinavians still have control of the sea. Knut conquered England & Norway.