Mordred

"My name... is Mordred."

- After Arthur asks for his name, Mordred says the words that Arthur should be afraid of.

Mordred was a young druid boy who was apprenticed to Cerdan and was taken in by Merlin and Morgana after he was separated from his father, Cerdan, in Camelot, who was ultimately executed by Uther Pendragon. Mordred formed a close bond with Morgana but eventually became an enemy of Merlin, whom he named "Emrys". Kilgharrah foresaw that Mordred would be responsible for the death of Arthur Pendragon.

It has been confirmed that Mordred will return in Series 4.

Biography
In the episode, "The Poisoned Chalice," Mordred is indirectly mentioned when Nimueh says to Arthur, "It is not your destiny to die at my hands."

After his master was turned over to the knights of Camelot, Mordred used his telepathy to call Merlin for help. Merlin helped him escape the guards and took him to Morgana, who offered to help Merlin hide the boy. Uther declared that anyone caught hiding the boy would be executed along with the child.

His arm had been wounded by the guards when they chased him through the town, and he fell sick after the wound became infected. Although Merlin tried to treat the wound, he was unsuccesful and was forced to tell Gaius that he and Morgana were hiding the boy from Uther. Gaius agreed to treat the boy, but would not help them return Mordred to the Druids.

Once Mordred was recovered, Merlin, Morgana and Gwen tried to sneak him out of Camalot; but Morgana was caught by Arthur and they were taken back to the castle.

They tried for a second time to sneak Mordred back to his people, this time with Arthur's help. Arthur, with Merlin and Morgana's help, managed to take Mordred back to the Druids where the boy finally revealed his name. Merlin almost allowed Mordred to be caught during the second attempt to sneak him out of Camelot due to the Dragon's prophecy, stating that Mordred was destined to kill Arthur, but eventually decided against this and helped him escape.

Morgana later mentions Merlin's help in Mordred's escape as her motivation for accompanying Merlin to Ealdor. (The Moment of Truth)

Return
When Morgana's magic started to reveal itself, she went to the Druids for help. Mordred informed his people of who she was and he helped care for her. But when Uther's soldiers raided the camp, Morgana was 'rescued' and Mordred was surrounded by several soldiers after briefly reuniting with Merlin. But, using a single spell, he knocked over, and possibly killed, the soldiers and escaped with the rest of his people. Merlin was visibly shaken by what he had witnessed Mordred do. (The Nightmare Begins)

In episode eleven, The Witch's Quickening, Mordred had sided with a group of bandits, led by a sorcerer named Alvarr. Morgana stole a crystal and delivered it to the camp, and Mordred was pleased to see her. Back in Camelot, Merlin visited the Great Dragon and he was told of an ancient prophecy foretelling an evil alliance between Mordred and Morgana. When Merlin and the soldiers attacked the camp, all were killed apart from Mordred, who escaped, and Alvarr, who was captured and later freed by Morgana. Merlin tried to stop Mordred from getting away by causing a branch to trip him, but Mordred used magic on two spears so as that they killed the two guards who were chasing him. Following this, Mordred looked over at Merlin and spoke to him in his mind, saying: "I shall never forgive this, Emrys, and I shall never forget." Then he ran into the woods, out of sight.

The Future
According to the Great Dragon, Mordred will eventually become evil and is destined to kill Arthur (The Beginning of the End).

It has been confirmed that Mordred will return in Series 4 and it is possible that he will team up with Morgana to make Merlin pay for betraying them.

In the official Series 4 trailer Mordred is faintly heard saying "Emrys" when Merlin gets pushed against a wall by magic and it is possible that Mordred is the one who pushes Merlin against the wall to take his revenge on him for his betrayal.

Personality
At first Mordred seemed to be an innocent child. He normally spoke telepathically and rarely communicated with his voice. Morgana even started to think he was mute, because he spoke so little. He was frightened whilst he was trapped in Camelot and when his father was executed Mordred sensed it even though he had not actually seen what had happened. Nonetheless Mordred revealed a dark and vengeful personality telling Merlin that he would never forgive or forget him after Merlin led Arthur and his knights to Mordred's camp and tried to stop him from escaping. He had a close bond with Morgana who was the only person besides Merlin and other magic users who was able to hear him speak telepathically.

Abilities
Mordred was powerful in magic and simply by screaming, both telepathically and with his voice, he was able to smash glass in Morgana's chambers and blast back two knights that surrounded him, either knocking them out or killing them. He was also able to levitate two spears and impale two guards without saying a word. Kilgharrah said that Mordred was possibly powerful enough to wield the crystal of Neahtid while Morgana was not.

Legends
Mordred is known as a notorious traitor who fought King Arthur at the Battle of Camlann, where he was killed and Arthur fatally wounded. In most versions of the legend, he is the illegitimate son of Arthur and his half-sister Morgause.