Dagr

Dagr was a thug whose income relied largely on profits from Mary's tavern. He had a band of followers, and one of them, Ebor, appeared to be his deputy. He was killed by Gwaine.

Revenge on Arthur
Dagr often came to Mary's tavern to take a share of the profits, threatening her with violence. On one such day, he was unhappy with how little he received, and upon holding a knife to her throat was challenged by a young stranger (who, unknown to him, was Prince Arthur). Upon being mocked by Merlin, Dagr called his men into the tavern, and a full fledge fist fight ensued. Arthur and his allies won, and Dagr was put in the stocks, desperate for revenge.

Dagr later obtained two Stulorne Blades and two crystals which would allow the bearer to take the form of whoever's blood they touched. He killed the seller and Sir Oswald, taking his form, and also killed Sir Ethan so Ebor could take his form. They planned to enter the melee and use the Stulorne Blades to get revenge, by killing Arthur.

Upon entering the citadel, Dagr was initially made a fool of by being forced to fight left-handed. He did, however, make up for this by ordering Merlin to do difficult and menial tasks. However, Merlin happened upon the blades, and came back in the night to investigate. Dagr almost killed him, but was rescued by Gwaine (who had come to Camelot by Arthur after he was wounded in the brawl), and eventually the fighting woke the guards. Gwaine was then banished, leaving Merlin to help Arthur on his own.

During the melee, the crowd noticed that Dagr and Ebor's swords were doing more damage than they should have done. However, a mysterious knight appeared (later revealed as Gwaine) to aid Arthur, and killed the pair. (Gwaine)