Morgana (Katie McGrath) is back with a vengeance in a SPINOFF-exclusive clip from this week's episode of Merlin in which she assures the enraged Queen Annis (guest star Lindsay Duncan of Rome fame) that she has the power to destroy the newly crowned King Arthur.

In "His Father's Son," Merlin and the Knights of the Round Table look on while Arthur’s judgment not only calls into question his leadership, but incurs the wrath of Annis, ruler of the Castle of Fyrien.  In her anger, she succumbs to the promises of Morgana that together they can defeat Arthur and claim Camelot.

Watch the exclusive scene below, and check out more clips and photos from the episode. Merlin airs Friday at 10 p.m. ET/PT on Syfy.