Season 4 of the medieval fantasy series Merlin premieres this Saturday, Jan. 7 at 8 p.m. ET, on Space.

The series follows the young wizard Merlin (Colin Morgan) as he discovers his gift of magic, working under the tutelage of court physician Gaius (Richard Wilson). Merlin must hide his developing skills as King Uther (Anthony Head) has banned magic in his kingdom, punishable by death.

In the Season 4 premiere, “The Darkest Hour (Part 1)”, Morgana, empowered with her magic stronger than ever, summons the mighty Callieach (Gemma Jones, Harry Potter and the Deathly Hallows: Part 2) to tear open the veil between the two worlds, effectively opening the gates to the Other World. Hellish creatures pour forth, killing any 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. Nothing will prepare Merlin when he discovers that the only way to restore the balance requires a sacrifice of unimaginable proportions.

This seaoson sees the return of Colin Morgan in the title role and Bradley James as Prince Arthur. The series also stars sci-fi and drama veteran Anthony Head as Lancelot, Angel Coulby as Gwen, Katie McGrath as Morgana, and Richard Wilson as Gaius.

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