Vortigern was a treacherous king of a small tribe who brought in foreign aid in an attempt to claim Britain for his own. He had drank the blood of a white dragon, lost his humanity, and become the very will and avatar of the Britain to fight against King Arthur. Believing that the coming Age of Man that was to wipe out the age of mystery would defile the island nation, he wished for it to fall, returning it to its original form and making it into hell, a "paradise of darkness no man can set forth in forever."
Vortigern is a dark figure whose armor has become black, having become a hole in the world. After losing his power, he is simply an old, dying man.
Vortigern is fundamentally opposed to humans ruling Britain, believing that it has no future so long as Artoria lives.
Garden of AvalonEdit
Garden of Avalon recounts the battle against Vortigern from Gawain's perspective. While Arthur was called a perfect and invincible king, the battle against Vortigern was one where defeat was very possible. Having cornered him in his citadel while fending off the foreigners, Artoria, Gawain, and her other elite troop made their way to the throne room where Vortigern was barricaded alone. Believing the battle to be won, they let their guard down and were overwhelmed by a single attack in their hesitation. It incinerated the troops, destroyed Gawain's morale, and took the light away from both Excalibur and Excalibur Galatine. Gawain could only watch as Artoria fought with Excalibur's faint light, never giving up even though she was fighting against Britain itself in the form of a dragon.
Destroying the citadel as he grew in size, Vortigern and Artoria fought for hours, and Gawain, finally regaining himself, could only beg her to retreat. She simply asked for his assistance with a smile, rejuvenating his spirit as they both fought the dragon. They were able to stall Vortigern by piercing their swords through his hands while Artoria pierced his heart with Rhongomyniad. Breaking the tyranny that had spewed from Vortigern, it left him as a feeble old man, calling them fools for granting Artoria the spear and saying they have brought forth greater ruin in order to defeat him. With his dying words, he claims that Artoria cannot save the kingdom because the coming of the age of civilization will mean the country has no future so long as she, whose power is at odds with humans, still lives.
Vortigern, having drank the blood of a dragon and become the very avatar of Britain, is a monster who even the powerful Knights of the Round Table could not imagine. Covered in darkness, he is a "hole in the world" that acts as a devourer of holy swords, the darkness growing thicker the holier its adversary. One attack is enough to incinerate a retinue of elite knights and bring Gawain and Artoria to the brink of defeat. There is a limit to the amount of light it can devour, causing Excalibur Galatine to fully lose its brilliance while Excalibur still retains the "glow of a weak bonfire."
He is able to fully become a dragon, increasing in size enough to destroy an entire citadel and engulfing a great amount of it with nothing but his neck. His roar is able to summon dark clouds. Standing against him is to stand against all the island of Britain, futile even to Artoria whose holy sword can burn the land. It requires the combined might of Artoria and Gawain to bring about a miracle to defeat him.