Myror took the place of Arthur's opponent in the joust, and Merlin had to use his magic to loosen the strap on his horse's saddle in order to save Arthur.

Caerleon was also very stubborn and proud as he refused to sign a peace treaty and appear weak, even when his life was threatened.

Inhabiting Cedric's body, Sigan animated the citadel's gargoyles and unleashed a raven-like monster to destroy Camelot, forcing Merlin to go to the Great Dragon for help. Finally Merlin and Arthur are able to free Gwen using a magic pool.

The series ended with Gwen and Arthur's wedding. Mordred saw Kara flee the scene of the Saxon attack and later met her in a forest and helped heal Kara's wound. If Merlin had listened to the Dragon once again, he would have eliminated a powerful threat, but he instead kept her alive. For the first time, Gwen sentenced someone to death. Tristan (portrayed by Ben Daniels) is the love of Isolde and her fellow smuggler. The servant in charge of looking after the castle's stables is suspected. Cipher manages to beat Pixy - symbolizing the Red Dragon's victory over the white dragon. Morgana finds an old dress of Gwen's in the camp and realises that Gwen has overheard her plans to invade Camelot. However, the fortress is soon alerted to the presence of an intruder, and the pair confront the unarmed king in the fortress. However, Merlin and Lancelot's deception was quickly discovered by Uther, who knew the man that Lancelot was claiming was his father, and the king ordered Lancelot's arrest. In "The Coming of Arthur, Part One", however, Morgause betrayed him by taking control of Cenred's army, which had just been made immortal via the Cup of Life, and ordered one of the soldiers to kill him. The dying sorcerer gives Arthur a coin from the Disir, interpreted as a judgement against Arthur. The troll's true form was subsequently exposed just after she was named as Uther's new heir, but the enchantment was so strong that Uther remained blind to her true appearance even after everyone else saw it and she could now show herself without fear. Cedric (portrayed by Mackenzie Crook) was a conman who set out to usurp Merlin's place as Arthur's manservant. The Dolma!". Merlin doesn't fully trust Mordred, a feeling echoed throughout the series. However Morgana often has doubts about Agravaine's abilities throughout Season 4 and is often seen threatening him and he in returns attempts to pacify her and assure Morgana of his abilities. He departed without saying goodbye, asking Merlin to tell her that "some things can never be".

However Merlin regains his magic and warns Arthur. She is the illegitimate daughter of Uther Pendragon and the half-sister of Arthur Pendragon and Morgause.

He took the realm by force and ruled competently for many years, creating prosperity for his people. He ran with them, carrying a sword. Mordred is telepathic and calls Merlin "Emrys" [the Welsh form of Ambrose or Ambrosius, meaning "Immortal"], claiming he knows who Merlin is and that they are "the same". When Prince Arthur came to defend Merlin's home village from raiders, Will initially accused Arthur of using the villagers as cannon fodder; however, Will eventually saw that Arthur was not afraid to risk his own life in battle. In the first episode, "The Darkest Hour, Part One", Arthur found Camelot under threat when Morgana sacrificed a dying Morgause to release the Dorocha, the spirits of the dead, to wreck her revenge on the kingdom. Although he has not used magic for years before Merlin's arrival in Camelot, Gaius has used spells since Merlin came into his life, such as using a spell to prepare an antidote when Merlin was poisoned and attempting to use magic to throw a weapon at Edwin Muirden (Although Edwin's magic proved more powerful than his), as well as occasionally assisting Merlin in treating injuries that can only be cured by magic.