Dark Souls Lore

Age of Fire III

Four centuries before the protagonist goes on a pilgrimage is Hawkeye Gough, Sir Knight Artorias and Puppy Sif going to Oolacile to destroy the darkness that was created by a primordial serpent, likely upstanding resident neighbourhood Darkstalker Kaathe, convincing the inhabitants to awaken Manus, Father of the Abyss. Artorias makes a pact with a great creature of the dark, likely another serpent, to become a beast himself thus allowing him to walk the abyss. Hawkeye Gough is caged by the remaining residents and his helmet's eye sockets stuffed with resin. Sir Knight Artorias and Puppy Sif journey to the Chasm of the Abyss, where Artorias' left hand is quite literally crushed, and Puppy Sif is cornered by humanity sprites. Artorias invokes the cleansing power of his bulwark of a shield, protecting Puppy Sif until someone comes trucking along, sound familiar? Anyway, Artorias is brutally murdered and converted into completely insane beast of the Abyss and left in the Arena of Stoicism.
Manus seeks a pendant, which two adventurers have the pieces to. Manus uses his great power to drag them through time and space, thus bringing Marvelous Chester and The Chosen Undead, the worst people he could possibly have imagined holding his pendant. Marvelous Chester seems to have been dragged from a time like Bloodborne, which is plausible.
The Chosen Undead brutally murders every single bloathead in Oolacile, and frees Puppy Sif from imminent death with the help of Alvina, who likely constructed the illusory wall that separated Puppy Sif from the other sprites, while leading the protagonist to it, without knowing she would eventually meet the same man in four hundred years. Manus is defeated, and the praise is given to Artorias, who is given the new champion name of Artorias the Abysswalker, which people from the Chosen Undead's time still think is alive and kicking, which in fact Artorias is very very dead by the hands of our truck-driver protagonist. Lord's Blade Ciaran comes along to mourn Artorias' death eventually, and possibly dies to our trucker because we want those sick tracers.

Around the same time, New Londo is flooded and the Four Kings sealed in the Abyss by the Sealers of New Londo. We see Ingward, someone who still thinks Artorias is alive, a corpse in Blighttown and likely a pillager of a Sealer accompanying Lautrec the Embraced of Carim.

Age of Fire IIII

Oscar of Astora, goes around the Asylum, freeing those he thinks are still sane. He manages to free our favourite upstanding-citizen truck-driving protagonist just before being smacked across the roof by the Asylum Demon.

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