We have the official Merlin synopses for the final two episodes of the third Series. The series concludes with another two-parter and it sounds pretty epic! Note these descriptions contain some big spoilers with several returning characters revealed and the introduction of another key figure from Arthurian lore.

The Coming of Arthur – Part 1 (airing Saturday 27 November at 7.45pm on BBC1)

Merlin and Arthur are sent on a dangerous mission to capture the Cup of Life, a powerful magical artifact that carries the gift of immortality.

But before they can retrieve the Cup, they are captured by unscrupulous slave trader, Jarl. A trusted friend comes to their rescue and they escape, but with Jarl’s help the cup falls into Morgause’s hands. With an immortal army at their disposal, will Morgause and Morgana topple Uther once and for all?

Merlin is played by Colin Morgan, Arthur by Bradley James, Uther Pendragon by Anthony Head, Gaius by Richard Wilson, Morgana by Katie McGrath, Gwen by Angel Coulby and the voice of the Dragon by John Hurt. Emilia Fox guest stars as Morgause, Tom Eliis as Cenred, Ralph Ineson as Jarl and Eoin Macken as Gwaine.

The Coming of Arthur – Part 2 (airing Saturday 4 December at 7.50pm on BBC1)

Newly crowned Queen Morgana begins a reign of terrible evil over the innocent citizens of Camelot as the fantasy series concludes with a dramatic finale. With Morgause’s immortal army at her command it seems there is no hope for Uther, who must watch his kingdom crumble under the unimaginable cruelty of his own daughter.

Meanwhile, on the outskirts of Camelot, Arthur regains his strength and, with Gwaine, Lancelot, Elyan and Percival at his side, plans a brave counter attack. But Merlin knows that even Arthur cannot vanquish an immortal foe. Can he reclaim the great sword Excalibur from the Lake of Avalon in time to save all those he holds most dear?

Queen Morgana is played by Katie McGrath, Morgause by Emilia Fox, Uther by Anthony Head, Arthur by Bradley James, Gwaine by Eoin Macken, Lancelot by Santiago Cabrera, Elyan by Adetomiwa Edun, Percival by Tom Hopper and Merlin by Colin Morgan.