(Disclaimer: Dark Souls’ lore is very vague in its description and a lot of it is left up to personal speculation. Below is my opinion. You are free to disagree with me if you wish. Also, MAJOR SPOILERS for Dark Souls ahead.)
I’ve chosen to do a look at Gwyn not because he has a long and detailed backstory, but because what story he has and how his story is told through Dark Souls is a great example of how a game like Dark Souls can really move you.
No one really knows where Gwyn came from, or anyone else before the battle with the Ancient Dragons. The histories simply begin there. The Ancient Dragons, clothed in primordial scales that granted them immortality, ruled over everything. The land was barren and desolate, with only giant arch-trees to give it any form. No other race could dare confront them.
Them came the primordial flame, and from it came the Souls of Lords. the Lord Souls where capable of giving the beings who possessed them great power. There where four Lord Souls, each representing a different aspect of the world. The four beings who seized the power of the Lord Souls where Nito, the First of the Dead, the Witch of Izalith and her Daughters of Chaos, Gwyn, Lord of Sunlight, and the furtive pigmy whom I shall get to in a minute.
With their combined powers, Nito, the Witch, and Gwyn struck down the Everlasting Dragons from their rule over the world. Thus began the age of fire where these beings pretty much became gods over the lands. They resided in Anor Londo, or the Land of Lords. There they stayed, rarely leaving their kingdom.
Elsewhere in the world the descendants of the pigmy became humanity. We spread, clashed, and eventually grew to be a power ourselves. Anor Londo was spoken of in legends and songs but few ever went there.
After some time, the lore doesn’t specify how long, the power of the Lords began to fade. The Age of Fire was coming to an end. The Abyss, a force of darkness that is not fully understood, had began to encroach on the Flame. It is unclear if the Abyss is truly evil or if there are things inside of it that are evil, however anyone who has gone into it has come back tainted.
It was around this time that the curse of the undead came into being. People began to come under the Darksign, a mysterious mark on their bodies which indicated that they would become undead. In this world, becoming undead is the first step to fully losing your humanity. After you become undead you are sent to an undead asylum where you await becoming hollow. When you’re hollow any bit of humanity or conscious or sanity has left.
Why was this happening? The humanity in our souls was needed to fuel the flame. Humanity was the remnant of the fourth Lord Soul, the Dark Soul. Humanity, as a whole, was also one of the Lords. By using this fuel the fire could be maintained for a short while. However, it was only a bandaid on the Titanic.
Eventually Gwyn knew that this solution would not work. The Flame was fading, and once it had burned out only darkness would remain. Gwyn decided to make the ultimate sacrifice. Gwyn went down to the Kiln of the First Flame, the home of the primordial Flame, and offered himself up to it.
Even with all of his power, this solution was only temporary as well. Gwyn had left in place a prophecy that an undead would come to Anor Londo who would collect the Lord Souls in order to fuel the first flame. The plan was that by the time this undead made it to the Kiln they would be truly powerful and a worthy offering to the Flame. More would be needed down the road, but as long as there was a patch then maybe the Abyss wouldn’t encroach any farther.
When the player, the chosen undead, finally reach the Kiln of the First Flame they meet Gwyn in combat. What is left of him is just a husk of his former self, the Flame burning away anything that made him more than that. No longer was he the Lord of Sunlight; he was the Lord of Cinder. At this point in the game the player is expecting an epic battle. Throughout the game the player has faced many challenges and has brought titans to their knees. In the end, they find themselves facing one of the easier bosses in the game. I’m not saying that Gwyn is easy, but he is a far cry from the rest of the game.
This is done to highlight the tragedy of Gwyn’s story. His only goal was to prolong the Age of Fire, to prolong his lineage’s place on the throne of the world, but every age comes to an end. After the battle ends, the player can choose to either offer themselves to the Flam in order to prolong the Age of Fire or to leave the Flame to die in order to bring about the Age of Dark. The game never specifies which one is the “good” ending, and this makes Gwyn’s sacrifice even more tragic.
The music to the fight with Gwyn. It does an excellent job at highlighting the tragedy of what Gwyn has become.