Merlin faces his toughest challenge yet when Morgana's blinkered determination
threatens not only Arthur's future, but also the very balance of the world. With
her magic stronger than ever, the sorceress summons the mighty Callieach to tear
open the veil between the worlds.

Hellish creatures pour forth, killing all who succumb to their touch. With Uther
a shadow of his former self, it falls to Arthur and his loyal knights, including
Lancelot, to protect the kingdom.

But it will take more than just swords to vanquish their enemy and Merlin is
shocked to the core when he discovers the only way to restore the equilibrium
requires a sacrifice of unimaginable proportions.

Starring: Colin Morgan (Merlin), Angel Coulby (Gwen), Bradley James (Arthur Pendragon),
Katie McGrath (Morgana), Anthony Head (Uther Pendragon), Richard Wilson (Gaius),
John Hurt (Voice of the Great Dragon)

Guest Starring: Santiago Cabrera (Sir Lancelot), Emilia Fox (Morgause),
Gemma Jones (The Cailleach), Nathaniel Parker (Agravaine), Rupert Young (Sir Leon),
Eoin Macken (Sir Gwaine), Adetomiwa Edun (Sir Elyan), Tom Hopper (Sir Percival),
Katie Moore (Drea), Zee Asha (Audrey), James Greene (Ferryman),
Charlie Petryszyn (Rescued Child), William Rowlands (Rescued Child),
Anya Davies (Rescued Child)

Creatures: Dorocha, Wyvren

Written by Julian Jones
Directed by Alice Troughton

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