 When Taran has been kidnapped, his companions Eilonwy, Fflewddur Fflam, and Prince Rhun enlist Gwystyl's aide in organizing an attack on Caer Cadarn, using additional supplies from Gwystyl's bag of magical tricks.They defeat Magg only because of Gwystyl's help.Much later, Gwystyl leads an army of Fair Folk reinforcements in the final days of climactic battle for the control of Prydain.