Merlin is told by the Great Dragon that it is his destiny to make sure that the young Prince Arthur is kept safe. Anybody caught performing magic is punished with death and Merlin is not a fan of Arthur. When Arthur's life is endangered Merlin finds himself tested.

A deadly plague spreads through Camelot. When it seems that sorcery can be the only possible explanation, Merlin and Gaius race to find a cure, while Gwen is arrested and sentenced to death for practising witchcraft.

When the Lady Morgana is struck down with a mysterious illness, Gaius is at a loss for a cure. Thankfully a new physician, Edwin Muirden is on hand to bring the King's ward back from the brink.

Uther's past comes back to haunt him as a mysterious Black Knight interrupts Arthur's coming-of-age celebrations, throwing down his gauntlet and challenging the Knights of Camelot to combat. The Black Knight, seemingly unstoppable, makes easy work of his combatants. But who is the Black Knight, and why is Uther so uneasy?

On a hunting trip, Arthur comes face to face with a creature of great power from the old religion. When Gaius informs them that it can only be killed by magic, Uther refuses to listen and sends out his knights to kill it. Arthur is fatally wounded and Merlin must go to the Isle of the Blessed to save him. But will he be able to pay the price?

New servant Cedric muscles in on Merlin's position as Arthur's right-hand man, and turns the prince against his loyal friend. Merlin is convinced the slippery newcomer is up to something, and he is right - Cedric is a conman and a thief who is after a magnificent jewel, recently unearthed in a tomb far beneath Camelot. Little does he know, his precious prize is more dangerous than he could possibly imagine.

Camelot has never been more vulnerable, but how can Merlin make things right when, thanks to Cedric, he might have lost Arthur's friendship for good? Merlin faces the prospect of turning to the one creature he swore he would never trust again - The Great Dragon.

Freya is found by Merlin trapped in a bounty hunter's cage and decides to try and help her escape. Merlin refuses to listen to Gaius' warnings not to get involved. After freeing her Merlin hides Freya in the tunnels beneath Camelot. Merlin is forced to make some hard decisions to keep Freya safe.

For the first time in over 300 years the fires of Idirsholas burn and Gaius is worried that a sorcerer has revived the deadly Knights of Medhir. Morgause returns and is determined to end Uther's reign at Camelot.

The Great Dragon is finally free. Full of rage, he attacks Camelot with pitiless intensity. The castle is crumbling and Arthur's men cannot hold out much longer but only a Dragonlord can kill a dragon and Uther wiped them all out years ago. Or did he? Gaius admits one such man could still be alive and in hiding.

The last Dragonlord is the key to Merlin's own past as well as the future of Camelot, but will Arthur and Merlin find Balinor in time to save the kingdom?

A year after her disappearance and when almost all hope is lost, Morgana returns to Camelot. While Merlin is afraid she might remember the circumstances of her disappearance and give him away in front of the king, a delighted Uther announces a banquet to celebrate. However, soon afterwards evil magic starts to take hold of the king's mind, putting the safety of Camelot at risk as he is consumed with hallucinations and enemies reach his door. Merlin suspects Morgana is behind the enchantment but his search for the truth puts his life in peril while Arthur is forced to take control and face new foes on his own. Will they succeed to rescue the king and Camelot from destruction?

With the help of the Great Dragon, Merlin manages to return to Camelot only to find out that is it on the verge of invasion: Morgause and Cenred have teamed up and plot against a weakened Uther. Cenred's initial reluctance is won over by the fact that they count on an ally within Camelot walls who will ensure the castle is taken. Uther is unable to rule which forces Arthur to step up front and defend the citadel agains Cenred's powerful army. With the help of Morgause and to make things worse, Morgana plays a deadly card and summons a skeleton army to wreak havoc within the castle walls. Camelot's fate rests once again on Arthur's shoulders and Merlin's magic as they fight in their own way to hold off both an army of the living and an army of the dead. Will they manage to succeed?

Merlin and Arthur find themselves outnumbered in a bar fight but an enigmatic young man helps them win. The man’s name is Gwaine and he risks his own life to protect Arthur but during his act of bravery he is seriously wounded. The Prince decides to take him back to Camelot where he could make a recovery with Gaius' help. Gwaine immediately gets to work: drinking, flirting with the ladies and causing lots of trouble for Merlin who has been instructed to look after him. However, when two unscrupulous knights seem to plot to murder the Prince, will Merlin and Gwaine be able to stop them and save Arthur?

After an unexpected meeting with the enigmatic old sorcerer Taliesin, the wizard takes Merlin to the crystal cave allowing him to witness a glimpse of the future. However, this gesture turns out to be more of a curse than a gift when, much to his horror, Merlin sees Morgana set to kill Uther. The young warlock knows he must do his best to try and stop the future from playing out. But changing the pages of destiny is a very dangerous game and his actions end up having fatal consequences. With the whole of Camelot in a state of grief, will Merlin be able to change the course of destiny and undo the damage he has caused, or will it be too late?

Arthur embarks alone on a quest to prove himself worthy of the Camelot throne by retrieving the Golden Trident from the Fisher King.

With the Prince beyond the protection of the citadel, Morgana takes the opportunity to use her dark magic. She gives him a precious bracelet that contains a Phoenix Eye, insisting that he wears it at all times for protection. However, the magical jewel takes away Arthur's life force and he is left defenceless in the Fisher King's perilous realm.

With the help of Gwaine, will Merlin be able to reach Arthur in time and fulfil his own quest to protect the future king of Camelot?

Camelot's legendary tournament only has one rule: there are no rules whatsoever. Terrifying warriors start to fill the mythical city, Gilli between them. Despite his small stature, Gilli is ready to join the action and committed to achieve victory with a secret weapon to help him: magic. When Gilli begins to realise the full extent of his powers, Merlin becomes torn since his new friend is putting his own life in danger as well as threatening the very heart of Camelot with his actions. Will Merlin be able to make Gilli see sense before it's too late?

Will Arthur be able to save Camelot from the evil Morgana? Morgana, newly crowned as Queen of Camelot, begins a reign of terrible evil over the innocent citizens of the kingdom. Counting on Morgause and her immortal army at her command all hope seems lost for Uther, who is forced to witness how his kingdom crumble under the unimaginable cruelty of his own daughter. Meanwhile, on the outskirts of Camelot, Arthur recovers his strength and plans a counter attack with the help of a few loyals at his side: Gwaine, Lancelot, Elyan and Percival. However, Merlin is aware that not even a skilful warrior like Arthur can defeat an immortal foe without magic. Will he be able to reclaim the great sword Excalibur from the Lake of Avalon in time to save the lives of those he cares the most about?

Evil sorceress Morgana summons mighty gatekeeper the Cailleach, who opens a door to another world from which hellish creatures pour forth. As Arthur and his loyal knights take up arms, Merlin discovers the only thing that will stop them is an unimaginable sacrifice.

The kingdom is on the brink of collapse and Morgana poised to strike, in the final part of this opening episode of the fantasy drama. As Lancelot races back to Camelot with the dying Merlin, Arthur must continue on his mission to vanquish the Dorocha without them. Though the Knights know their journey to the Isle of the Blessed is fraught with danger, none could anticipate the sacrifice Arthur intends to make there.

Friendship and loyalty are tested to the limit, but in the end, it's the power of love that changes all their lives for ever.

A mysterious visitor arrives in Camelot seeking a very special prize: a dragon's egg.

Morgana joins forces with enigmatic wizard Alator to uncover a secret that could change the course of destiny, as the magical drama continues. With allies on both sides of the castle walls, can anyone stop her before Merlin's greatest secret is revealed?

Morgana and Helios have successfully captured Camelot, and Merlin and Arthur are outlaws on the run, in the last episode in this season of Merlin. Trapped in Ealdor with a ruthless army closing in, their situation becomes desperate. Arthur must take control before Camelot is lost forever… But faced with Agravaine’s betrayal and the strength of Morgana’s force, the young King has lost his conviction. Only Merlin can restore his faith, and only an extraordinary act can prove to the King that he was born to rule. Will the young warlock convince Arthur before his dreams of Albion fall to pieces?

When Gwen is snatched from Camelot without warning, Merlin knows there can be only one person responsible: Morgana. Arthur is determined to rescue his Queen – but it's not going to be easy, for she is locked in the Dark Tower, a place that haunts the dreams of men.

Arthur and his Knights must embark on a quest like no other, battling through a landscape riddled with hidden dangers, perilous obstacles and magical beings. As they near their goal, Merlin's sense of dread reaches breaking point. What twisted game is Morgana playing? And more importantly, just what is the final test that awaits them in the tower?

When Merlin agrees to help a young Druid boy, he has no choice but to leave Camelot on a dangerous mission.

And with the citadel distracted by the visit of the fearsome Sarrum of Amata, it seems that no one will notice his absence.

But as the sky darkens, so do Merlin's suspicions - is there more to Daegal than meets the eye? And can a man as ruthless as the Sarrum ever really be trusted? Too late, the young warlock realises he's made a terrible mistake.

Mordred finds himself torn between loyalty and love, but little does he realise that the path he chooses will shape Camelot's destiny.

As the drums of war beat ever louder, a desperate Merlin feels trapped by the cruel circle of fate - is he powerless to stop his dreams of Albion from crumbling to dust?