Lands of Mystery
Sword and Sorcery
The DMG describes the Sword and Sorcery subgenre:
A grim, hulking fighter disembowels the high priest of the serpent god on his own altar. A laughing rogue spends ill-gotten gains on cheap wine in filthy taverns. Hardy adventurerers venture into the unexplored jungle in search of the fabled City of Golden Masks. A swords-and-sorcery campaign is old-school D&D, a tradition that goes right back to the roots of the game. Here you’ll find a dark, gritty world of evil sorcerers and decadent cities, where the protagonists are more motivated by greed and self-interest than by altruistic virtue. Martial characters tend to be far more common than arcane or divine ones. In such a pulp fantasy setting, those who wield magic often symbolize the decadence and corruption of civilization.
The theme of the campaign will follow this model. I imagine a more ancient, more brutal world than a typical D&D game. “Might makes right” is the law of the land instead of chivalry. Isolated city-states replace kingdoms, and they are ruled by tyrants, not wise and benevolent nobility. Gods and other supernatural forces use mortals as pawns in their petty and sometimes cruel games.
Conan (stories by Robert E. Howard), Beowulf, King Arthur (movie and legends), Celtic myths, Norse myths, 300, God of War