Mordred

Sir Mordred the Mad was his full name. He was second-in-command to Artorias in the Order of Dusk. Mordred served as a dirty hand for the town's needs and Temple of Dusk related activities. His loyalty was never in question, but his piety was elastic.

Secretly, he was in a romantic relationship with the Court Enchantress Morgana Le Bae. She began breaking his loyalty to Artorias and Gwyn by speaking of fantasies where Mordred was King of Gwynneth.

The birth of Artorias' son Gawain, the new prince, fed into Mordred's dark fantasies now running rampant thanks to Morgana.

On the mission to investigate the Temple of Dusk, Mordred gave in fully to Morgana's dark enchantments and his own brooding jealousy. On multiple occasions he tried to engineer Artorias' death with the secret help of Morgana and Sir Locke.

When Morgana openly betrayed Artorias, Mordred sided with his enchanting lover. In raging koala form, he reigned down a furry flurry of blows that knocked his brother-in-arms unconscious.

Inside the ritual room, the child on the altar turned out to be a secret spawn of his romantic liaisons with Morgana. She herself had been betrayed by Bane. The child's name was Oberon and became cursed in Morgana's desperate revenge against all.

After the ritual was interrupted and Sir Locke revealed he had drunk from the fountain of black ooze, claiming to be The Black Knight, Mordred went into a rage attacking both Locke and Bane.

In the final moments of battle, when the whole world was crumbling down in the ritual room, Mordred grappled with Bane and attempted to push him into the yawning portal that Dusk herself was controlling. Morgana, seeing her spurned koala lover locked in arms with the God of Tyranny, let loose a thunderous boom that launched both Mordred and Bane into the portal.

What happened to Sir Mordred the Mad after that is unknown.

It was rumored that he was the real father of Sir Locke.