Mordred

"Are you telling me that little boy's going to kill Arthur?"

- Merlin

Mordred is a young druid boy who was taken in by Merlin and Morgana after he was seperated from his father, Cerdan, in Camelot, who was ultimately executed by Uther Pendragon.

Mordred is a user of magic, specifically telepathy and used these abilities to call Merlin for help. Merlin helped him escape the guards and they hid in Morgana's room, who offered to help Merlin hide the boy. Uther declared that anyone caught hiding the boy would be executed along with the child.

He was 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 ultimately 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 to return Mordred to the Druids.

Once Mordred was recovered Merlin, Morgana and Gwen tried to sneak him back to his people 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 when Mordred grows up he will 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)

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 allience 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.

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

Mordred is not set to reappear in Series 3.

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 hadn't actually seen what had happened. Nonetheless Mordred had a dark and vengeful personality telling Merlin that he would never forgive or forget him after Merlin led Arthur and his knights to Mordreds 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. Mordred also seemed to have an almost father and son relationship with Alvarr.

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 weild the crystal of Neahtid while Morgana was not.