In the Age of Ancients,
The world was unformed, shrouded by fog
A land of grey crags, archtrees, and everlasting dragons
But then there was Fire
And with Fire came Disparity. Heat and cold, life and death, and of course.. Light and Dark.
Then, from the Dark, They came
And found the Souls of Lords within the flame.
Nito, the first of the dead
The Witch of Izalith, and her daughters of chaos
Gwyn, the Lord of Sunlight, and his faithful knights
And the furtive pygmy, so easily forgotten
With the Strength of Lords, they challenged the dragons.
Gwyn's mighty bolts peeled apart their stone scales
The witches weaved great firestorms
Nito unleashed a miasma of death and disease
And Seath the Scaleless betrayed his own, and the dragons were no more
Thus began the Age of Fire
But soon, the flames will fade, and only Dark will remain
Even now, there are only embers, and man sees not light, but only endless nights
And amongst the living are seen, carriers of the accursed Darksign.
Introduction (SPOILER WARNING!!! Do not read further if you wish to discover things for yourself!)
You are the Undead, one of many doomed to live forever in the Undead Asylum until the end of the world. However in ancient legends, one undead is chosen to make pilgrimage to the land of the ancient Lords, Lordran.
After being given help in escaping your cell, you must retrieve your equipment and escape the Asylum by killing the Asylum Demon. Once you leave the Asylum you are taken to Firelink Shrine, where you are tasked by the Crestfallen Warrior to ring the two Bells of Awakening, one in the Undead Parish and one in Blighttown. Each Bell is guarded by it's own guardian, the Belfry Gargoyles guard the Parish and Chaos Witch Quelaag guards Blighttown.
Retrieving the Lordvessel
After these bells have been rung, Kingseeker Frampt awakens from his slumber in the Firelink Altar. He explains that you are the Undead who has been chosen to succeed Lord Gwyn in the Kiln of the First Flame. To do this, you must first travel through Sen's Fortress to Anor Londo so that you can retrieve the Lordvessel. Sen's Fortress is a nest of walkways and booby traps patrolled by Serpent Warriors and at the top of the fortress, the Iron Golem stands watch over the entrance to Anor Londo. Once you have defeated him and made it into Anor Londo, you must fight through Princess Gwynevere's Silver Knights and Sentinels to face Dragon Slayer Ornstein and Executioner Smough, who guard Gwynevere's chamber. After they are defeated, you are gifted the Lordvessel which you must now place on the Firelink Altar.
Gathering the Lord Souls
Frampt now tells you that to gain an audience with Gwyn, you must gather the Lord Souls from the other keepers and offer them at the Altar. These keepers are: Seath the Scaleless, Gravelord Nito, the Bed of Chaos and the Four Kings. Seath the Scaleless was Gwyn's advisor but after being driven insane he was locked away in his archives, surrounded by a crystal army. Gravelord Nito resides in his coffin in the Tomb of the Giants, watching over the dead. The Bed of Chaos was accidentally created by the Witch of Izalith before she was engulfed by it while attempting to recreate the First Flame. The Four Kings were recognised by Lord Gwyn and gifted pieces of the Lord Soul, but soon after succumbed to the Dark.
Linking the Fire OR The Age of Dark
Once all the Lord Souls are offered, you enter the Kiln of the First Flame, where Lord Gwyn and his faithful Black Knights keep the First Flame from dying out. However you must kill Gwyn to succeed him and afterwards you are given the decision to either link the fire, keeping the Age of Fire going by offering yourself to the fire and prolonging everyone's lives with the gods still in charge, or start an Age of Dark, letting the flame go out and becoming ruler of the new world.