According to the BBC press office:
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.
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Can Arthur (Bradley James) save Camelot from the evil Morgana?
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.
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Still wondering HOW Morgana makes it onto the throne, how Uther is got out of the way despite apparently still being alive, how Arthur is seperated from the court or where Gwen is in all of this - let alone whether Arthur now knows that he's related to Morgana.
I'm kind of looking forward to seeing Uther confronted with what he's created in Morgana, although whether or not he'll be able to acknowledge that it was his combined actions as king - disowning Morgana and starting a genocide - that primed events to turn Morgana into the little psycho she's apparently become, is another matter (whether the SHOW will want to deal with that idea or portray him more sympathetically is in question too. 'Scuse my cynical feminist leanings but Merlin has always seemed very reluctant to hold male characters accountable for their actions when a female one can just be blamed because she's 'evil'...)
Loving that Katie McGrath is credited as 'Queen Morgana', irritated that Angel Coulby/Gwen is missing from the credits even though we KNOW from filming pics that she's likely to play a significant part in events to come and Elyan/Adetomiwa is in there too. Wondering how or even whether Morgana will be able to stay on as a regular cast member after this given that her ninja!evil ways are pretty clearly not going to be quite so ninja by the time the season comes to an end. Either way - LOOKS KIND OF EPIC, MULTIS. What do you guys think?