From the introduction:
In a gray and changeless time, where stone-scaled dragons ruled over all things, four beings found godly power within the flames. Three of these became as gods to the other residents of the world as they cast down their dragon overlords, with the help of a vengeful dragon outcast, slaying them with the power of lightning, fire, and death... One, however, disappeared from the annals of history.
The fourth, the Furtive Pygmy, remains a mystery throughout the war with the dragons and the Age of Fire that followed. It is rumored, however, that humanity itself is the offspring of the Pygmy, bearer of the Dark Soul. The other four, the dragon outcast Seath the Scaleless, the Witch of Izalith, Nito the Gravelord, and Gwyn, Lord of Sunlight, ruled as gods in the land of Lordran.