Lloyd Alexander creates complex, not one dimensional villains. Prince Ellidyr and Taran dislike each other from the start. They both want to run the show. Ellidyr is a foil to Taran who eventually sees his own desires in him, even recognizing the same folly that drives the prince drives him as well. He learns that it is easy to "judge evil unmixed," but more difficult to look at it honestly. "I taunted him for seeking glory yet cling to it myself," Taran says in a moment of truthfulness. The two fight ruthlessly at first and goad each other, but eventually Taran starts to exercise self-control and ignore Ellidyr. He tries to make peace with him but Ellidyr will not agree to it.
This overarching theme of a hero's honor is explored in great depth. Ellidyr calls Taran pig-boy to insult him and later when Taran begins to believe it, Eilonwy scolds him. She points out his honorable actions in being responsible as an Assistant Pig-keeper. Taran mulls it over and decides that honor doesn't come from the praise of others but from doing deeds for ones own self. Tied in this is the message of sacrifice. Aadon, sacrifices for the good of the group as does Ellidyr. Even though most of Ellidyr's actions were dishonorable, in the end he redeemed himself with honor.
When Taran is given a magical brooch, it teaches him empathy, especially with Ellidry, the son of an impoverished king, who wanted fame so much he was willing to kill Taran. He understands his need for glory and self-identity, but unlike Ellidry, Taran realizes that he can't seek it from other people. When he gives up the brooch, he realizes that he can't rely on magic to be a hero, but must rely on himself. "You chose to be a hero not through enchantment but through your own manhood." He learns that sacrifice means giving up his most treasured possession.
Alexander shows that Ellidry's choices have made him a complex, unlikable character; yet he is a sympathetic character because the reader understands Ellidry's misplaced motivations to make a name for himself in the world. The mysterious enchantresses, Orddu, Orgoch, and Orwen, appear evil, but their actions show otherwise. Taran is learning that first impressions are not always correct and that peoples actions show true character. Taran starts to consult Eilonwy during the quest, something he didn't do in book one. He is beginning to respect her opinion and get her input. He grows the most in this tale and is beginning to take a romantic interest in Eilonwy.
The struggle to achieve competence and find one's self-identity is a part of growing up. Good literature reflects heroes that achieve particular feats by accomplishing those feats on their own. It shows the child protagonist growing into a competent, independent adult. This is a common theme in stories for children that feature an inhibited child or impulsive child or scatterbrained child that learns to be competent in an area so as to gain skills and wisdom that will help him or her grow up. Taran also learns ethics and what it means to be a good person in an evil world. This message of achieving moral values externally and internally is timeless and worthwhile. I can see why this story won the Newbery Honor medal in the 1960's.