FromSoft’s Souls games are infamous for their vague story. Ultimately, it’s about the player trying to make their way from point A to point B while killing anything big enough to stand in their way. After awhile, you kill these obstacles until there’s nothing left to kill – then the credits roll and you start NG+.
But what lies below the hellish difficulty is a world full of deep lore that can be learned about through item descriptions, architecture, and NPC dialogue. While this explanation is all but comprehensive, it will explain the overall narrative of the original Dark Souls.