Dark Souls 3 - Oolacile, The Abyss and New Londo - Gaming World

Oolacile, The Abyss and New Londo

    The Furtive Pigmy took the Dark Soul and gave birth to mankind. When the Flame started to fade, the Lord Souls taken by the gods started to lose power, while the humans born from the Dark Soul started becoming stronger. Gwyn feared that some day humans would take over and annhilate the Gods, just as Gods killed the Everlasting Dragons, which would lead to another change in the order of the world's leading race. Without linking the fire, the world would descend into an age of darkness--an age of men--where the Dark Soul rules. Gwyn, fearing this religation of Gods, chose to link the fire to prevent this age of darkness.
Speculation*: The Dark Sign is a curse Gwyn casted to humanity when he linked the fire for the first time. This is believed because the curse did not show up the first time the fire was fading, and started only after the fire was kindled by Gwyn and fading again.
The sorcerers of Oolacile were tricked by the Primordial Serpent Kaathe into disturbing the Primeval Human Manus. Upon awakening him, Manus' humananity went wild and began to consume Oolacile, thus creating the Abyss. Manus also took Princess Dusk captive. Gwyn's Knight Artorias tried to defeat Manus but he was overpowered and corrupted by the Abyss. Manus is eventually defeated and his Soul Shatters creating Humanity Sprites for the Undead as well as birthing his Daughter/Shards.
The Abyss did not exist until the events that took place in Oolacile,  born only after Manus' humanity went wild due to torture. Humanity is described as something warm as well as dangerous, and when it was disturbed it created the Abyss. Artorias travelled to Oolacile in order to stop the spread of the Abyss. It is stated in Artorias' ring that he made a pact with the creatures of the abyss not to be corrupted and killed. This is key because we are told that humanity is born from the dark soul, which implies darkness. However, the darkness--whether of the Dark Soul or Humanity--is shown not to be inneherntly evil, but rather torture and maltreatment of the darkness created the Abyss. The Abyss corrupts everything and kills everyone, but it seems that some creatures inhabit this peculiar place.  It appears as though the disruption of the Lord Souls (or fragments of it) create monstruosities. The Witch of Izalith tried to create a First Flame with her own Lord Soul and it lead to the creation of Chaos. Oolacile's people disrupted a fragment of the Dark Soul ( Manus) and formed the Abyss.
Once the Abyss came into being, Kaathe seduced the Kings of New Londo into becoming Dark Wraiths and learn the Art of Lifedrain, so that they may gather humanities to rebuild the Dark Soul. Some Kaathe dialogue:
Ahh… If you wish, I shall grant the art of Lifedrain, the legendary power of the Dark Lord. It can preserve your humanity while Undead, and cast off the shackles placed upon your brethren.
After realizing the threat that the four Kings carried over to the entire world, Gwyn ordered to flood New Londo, leaving countless humans dead under the water. 

The Chosen Undead 

     "Only, in the ancient legends it is stated, that one day an undead shall be chosen to leave the undead asylum, in pilgrimage, to the land of ancient lords, Lordran."
Years pass since Gwyn has Linked the First Flame and it has once again begun to fade.  Legends state that a Chosen Undead will rise up and succeed Gwyn to Relink the Flame.  One such Undead Succeeds where many have failed.  The Chosen Undead collects the 3 Lord Souls and their Shards and journey's to the Kiln of the First Flame defeating a hollowed Gwyn.  It is uncertain if the Flame was relinked or not, but many others have ventured forth to do so.
This legend of the chosen undead could have been created by the Gods themselves, in order to extend their age of fire.