Demon's Souls is set in a fictional dark fantasy world, taking part mostly in the southern medieval kingdom of Boletaria, that has been consumed by a thick, mysterious Fog that is creeping ever out to blanket the entire world. The Old One, a colossal immortal flying Demon, has been awoken and with it Demons have come forth to consume the souls of men. Only when The Old One is lulled back to eternal slumber will the fog dissipate and the world be restored.