The film's main villain initially had to be Arawn, but animators felt that the Horned King would have been better received by the audience since he had horns (like Maleficent and Chernabog, two appreciated villains before him). So they combined elements of the two characters in order to create a lich, even if the narrator implies that the spirit in the Cauldron is Arawn himself.
The Horned King is one of the most ruthless and merciless villains in the Disney Universe. He's cold and very collected, only showing anger when his plan fails and at that point he throws himself at Taran, believing it was his fault (under Creeper's suggestion). He's quite mysterious, and it's implied that not even his underlings know what he is, and he's one of the few active villains, his only move in the movie (that is not done by his servants) is his role in the awakening of the Cauldron Born. Also, he has no secrets about his intentions, he's very open about his dream of becoming "a god between mortal men." He shows no sense of humor or makes evil laughs, and the only time he does so, it is scornful and sarcastic.
The Horned King is a skeletal creature with green, rotting flesh and two gnarled horns from which he earns his name. It is debatable whether the Horned King was undead or living; since Creeper served him wine at some point during the film, it can be assumed he possesses a digestive tract, implying he is a living being or at least that he is still able to enjoy food and drink. It is possible that in his quest for power, he tried several dark magical approaches, which left his physical appearance deteriorating.
It is also possible that in his obsession with godhood, the king has used his magical abilities to stave off death but is unable to keep his body from deteriorating as he is a skeletal creature with rotting flesh. Nevertheless, the decomposition seems only external as he is physically strong, fast and agile and able to project his voice.
Powers and abilities
Although it is implied the Horned King is a sorcerer of some sort, he actually performs very little magic, only displaying his powers to teleport into his castle's mess hall and calling upon the spirit of the Black Cauldron. How he became King is unknown. Perhaps he was a great warrior or soldier, but then again he is never seen wielding a sword. He did have great physical strength, however, as he used that to assault Taran in the climax.
“No! You'll not have me! My power cannot die! Curse you! No! No!”
―The Horned King's last words
The Horned King desires to find the Black Cauldron and use its power to unleash an army of deathless Cauldron Born to rule the world. He goes to many lengths to find it, kidnapping Princess Eilonwy for her bauble and the pig Hen Wen because he believes they have powers to locate the Black Cauldron. He is first seen talking to his currently non-animated Cauldron Born on his goals. He is seen again when he enters the mess hall of his castle via magical teleportation. There, Creeper tells him they are celebrating their success in capturing the pig. When the assistant pig-keeper Taran falls into the room whilst attempting to rescue Hen Wen, the Horned King instructs him to show the location of the Black Cauldron via the pig. When Taran refuses, the king claims the pig is no longer of use to him and orders his men to kill it, forcing the boy to comply. As Taran instructs Hen Wen to create a spell pointing the Cauldron's whereabouts, the excited king gets too close to Taran, who in his fright splashes water into the King's eyes (which has an agonizing effect on him) to lead Hen Wen into a chase where they manage to keep Hen Wen away after Taran throws the pig into a moat. However, Creeper drags Taran to the Horned King, who is angry about Hen Wen's escape and orders Taran to be thrown into the dungeon.
Later, Creeper reports that Taran and his new company have escaped, which he thinks will result in him being strangled, so he attempts to do it himself. However, the Horned King congratulates him, as the trio will undoubtedly locate the Black Cauldron, and quietly tells him to send the Gwythaints to follow them. The three are ultimately captured along with the newly acquired Black Cauldron which he then uses to summon the Cauldron Born. He sends them to destroy all opposition, however Gurgi arrives, frees the prisoners, and flings himself into the Cauldron to negate its necromancy ability. The Horned King suspects Creeper is the one to blame and carries him, returns to the room where the ritual was performed and finds Taran who he believes the Cauldron's failure was his doing. He throws Creeper aside, grabs Taran, and lifts him off his feet, but Taran pushes the Horned King into the pull of the Cauldron. The Horned King grabs Taran again and tries to throw him into the Black Cauldron, but the cauldron pulls the Horned King in instead and rips him to a skeleton, and explodes. The Horned King dies, and his castle soon follows.
The Horned King makes appearances in several episodes of House of Mouse. He is also notable to be one of the only characters from The Black Cauldron to appear in the series along with the Cauldron Born.
The Horned King is the final boss in the heart of Cinderella's castle, using his black cauldron to summon Cauldron Born skeletons with the intent of overrunning Tokyo Disneyland. It is unknown how he arose, but it is possible this was Pete's fault for messing about with his black cauldron in Mickey's Great Adventure in Tokyo Disneyland.
The Horned King appeared as an audio animatronic in the Tokyo Disneyland attraction, Cinderella Castle Mystery Tour. In this tour style walk through attraction, the Horned King is the final Disney villain the guests confront. The tour guide will tell a guest the magic words to defeat the Horned King and his Cauldron Born army. At the end of the tour, the guest was awarded a medal for defeating him. The attraction served as inspiration for the final level of a Tokyo Disneyland-based game on the Super Famicom where Pete played the part of the Horned King. This attraction closed in 2006 and the animatronic has not been used or seen by guests since the closure.
During his death, the Horned King's scream keeps being heard a little time after his body has been entirely destroyed. It might be an animation mistake, but it is also possible that it is meant to imply that he is screaming from his very soul.
The Horned King is definitely considered one of the darkest, pure evilest, and most serious Disney animated villains, as he never has redeeming qualities nor he makes any kind of joke (his taunting of Taran, Eilonwy, and Fflewddur Fflam notwithstanding) and he always maintains his frightening and villainous image no matter what the situation.
The Horned King is one of the few villains without a song. The Horned King is accompanied by a haunting leitmotif composed by the late Elmer Bernstein.
The Horned King in the original book wasn't the main villain but rather the most powerful minion of the book's true villain Arawn. He is defeated off-page when Prince Gwydion discovers his True Name and uses it to destroy him.
In the Italian version of The Black Cauldron, the Horned King was called "Re Cornelius" ("King Cornelius", most likely after the fact that the similar-sounding "corno" means "horn") because the Italian word for "horned" ("cornuto") also vulgarly means "a person that has been betrayed by the proper partner". For the same reason, in the French version, he is renamed "le Seigneur des Ténèbres" ("the Lord of Darkness"). This may create slight confusion when, at the beginning, in Taran's daydream, the goat represents the Horned King.
In spite of the film's lack of success, the Horned King could perhaps be recognized as one of the most popular Disney animated villains ever; he is classified as an official member of the Disney Villains franchise and has made appearances in House of Mouse, alongside his undead minions the Cauldron Born, albeit he may not necessarily be qualified to fall under a recognized status.
His late voice actor, John Hurt, sounds like Victor Caroli, the narrator of the 80s Transformers cartoon and the voice of Tirac, the equally dark pure evil villain of G1 My Little Pony.
The Horned King has one of the most brutal and graphic deaths in an animated Disney film, as his skin is sucked off his bones onscreen.