lore so deep i cant see the surface anymore

the serpents came by opening the abyss and took the humans (at the time all hollows) out with them
first flame didnt create disparity, the abyss did (shadow caused light, its simple)
serpents' goal was getting rid of the dragons and they used the humans the first flame, which at the time was the epitome of life force, to do that
reason was their jealousy, serpents literally represent jealousy/avarice in dark souls

these 4 points arent a time line, just the factors making up the beginning of dark souls' lore

dragons die, serpents win, manipulate humans into continuing the cycle either by linking the flame or ignoring it until someone else links it, same thing to them
after dragons are dead they arent done with their jealousy, they want to become dragons in a strive for perfection (see covetous rings das1)
pilgrims are the result of their pursuit  https://gyazo.com/9ad4e5ceb8ec156283f0e36800c110a1
ashen one is different for whatever reason and worthy of ending the cycle by usurping the first flame. proably different cause he has no inner fire and works as a vessel, maybe because he became cursed with the sign of the undead after dying and thus lives with no life or something (berserk references all over here)

serpents are the beings of the abyss, humans too, kinda, dragons are neutrals, angels are beings of the light and the last piece in the puzzle