The High King is about the ultimate battle between good and evil. When the magical sword, Dyrnwyn, is taken from Gwydion by the death-lord Arawn, Taran and the companions are forced to gather armies to attack the evil lord’s fortress to get it back. After being made a war lord, Taran leads his armies to Caer Dathyl, the Sons of Don capital. After a bitter betrayal Caer Dathyl lay in ruins and the survivors head towards Arawn’s fortress. Once Taran’s band gets there from the mountains, Taran finds the sword while defending himself. He then uses it to destroy the immortal enemy warriors, the Cauldron Born. Once defeated, the other enemy warriors are subdued and the Castle is captured. Arawn, after killing the enchantress Achren, is brought down by Drynwyn. Then the Sons of Don sail away to the land they came from and Taran is made the new High King.