Dark souls is a mysterious setting. Lore of the world, people and its history are given through small intricate details, world design, and the minimal amount of dialogue with NPC's. Many of the items in Dark souls that the player can pick will have descriptions that make up a small part of the story. One would have to go out of their way to attempt to understand the lore. With that being said, there's still a basic plot the first game follows. It can best be summarized with the opening cutscene.
The creator of Dark souls Hidetaki Miyazaki was heavily inspired by western mythology as well as Japan's mythology so it's only reasonable that his game contains refrences to these sources. In Dark Souls there is a reaccuring setting of the city of the Gods, Anor Londo that sits atopt a mountain peak. This can be linked to Mount Olympus in Greek mythology which also served as a home atop a mountain for the Gods to live. From mythology in Japan, the dark souls boss Quelaag serves as just one example. She is based off the Japanese myth of the Jorōgumo, a spider that takes the form of a women to trick and ensnare people. She appears in the game as beautiful women with a lower body of a giant spider. Gravelord Nito is very much a representative of a God of death much like hades or how we view death as a character. Then there is the common use of Dragons which has various depiction across mythologies around the world.