The protagonist of the series, Taran is the Assistant Pig-Keeper of Caer Dallben, charged with caring for the oracular pig, Hen Wen. Taran is dissatisfied with this life of tedious drudgery and would prefer to have exciting adventures like his idol, Prince Gwydion. Over the course of the series, Taran is caught up in many battles for Prydain’s future, but the heart of the story is more focused on Taran’s own personal journey, and he undergoes an enormous amount of Character Development as he grows from a boy to a man.
Aesop Amnesia: At the end of The Book of Three, Taran learns that grand adventures are far more dangerous than he thought and that he was ill-prepared for the trials he had to face, and he much preferred living a peaceful life at Caer Dallben. At the beginning of The Black Cauldron, he is back to being a Heroic Wannabe again. Thankfully, the lessons stick this time.
Being Good Sucks: Doing the right thing for Taran always requires sacrifice, and very often demands that he give up the things that are most important to him, often with little thanks or reward. He does it anyway.
Coming of Age Story: This series is as much about Taran growing up as it is about cool adventures in a high fantasy world, if not more so.
Cool Horse: Melynlas, the son of Prince Gwydion’s own steed, Melyngar, is gifted to Taran in the first book, and serves his master faithfully for the rest of the series. Melynlas only allows Taran (and sometimes Eilonwy) to ride him.
Cool Sword: Dallben gives him one early in the second book. Taran assumes it is enchanted, a notion Dallben finds fairly repugnant. Later in the series, Taran loses this blade and forges his own sword, and eventually earns the right to wield Dyrnwyn in battle.
Earn Your Happy Ending: After numerous painful sacrifices on his part, including giving up a chance at eternal happiness in paradise, the series ends with Taran marrying Eilonwy and becoming a wise and respected ruler.
Embarrassing Middle Name: His official title is Taran, Assistant Pig-Keeper. However, Hen Wen is a very important pig, and Taran takes great pride in caring for her.
The Everyman: Taran is never physically described and meant to be very easy for a young audience to identify with.
Fearless Fool: In the first book, and to some degree in the second one. However, though he never really loses his gung-ho attitude, he gets a lot less foolish about it as the series progresses.
Friend to All Living Things: While not as blatant as other versions of this trope, Taran is shown on many occasions to have a very strong kinship with animals, especially Hen Wen. He is capable of taming even a savage gwythaint fledgling, and his horse, Melynlas, obeys his commands alone. Even Medwyn is impressed.
Glory Hound: Early on, Taran wishes to make a name for himself and be a hero. This is a major plot point in the second book.
Guile Hero: He spends as much time of the fourth book solving problems through his own cleverness as he does with violence.
Does Not Like Shoes: Eilonwy is either barefoot (The Castle of Llyr) or wearing sandals (The Book of Three).
Everything's Better with Princesses: Amusingly, the fact that Eilonwy is a princess is revealed only in passing near the end of the first book, and doesn’t become a plot point until the third.
Fiery Redhead: The narrator often identifies her as "Eilonwy of the red-gold hair." The supplemental volume The Foundling and Other Tales of Prydain confirms that she inherited her hair color from her mother, Princess Angharad, who was a greeneyed redhead.
A strange, shaggy forest creature who speaks in third person and uses a lot of rhymes, Gurgi is neither man nor beast. At first, Gurgi is a miserable coward who flees at the first sign of danger, but as the series goes on he grows to become brave and loyal. He comes to admire Taran for his wisdom, and eventually becomes his closest friend.
Big Eater: If he's not hungry, then something is probably seriously wrong.
Rhymes on a Dime: A peculiar version, as he doesn't actually speaks in rhyme, but rather peppers his speech with rhymed pairs of words, such as "crunchings and munchings" (= food), "smackings and whackings" (= beating) and "sneakings and peekings" (= spying).
A loud-mouthed bard who tells exaggeratedly wild tales of his own acts of heroism, Fflewddur is a good-hearted if overzealous adventurer who frequently accompanies Taran on his quests. It is quickly revealed that he is not actually a real bard, but is actually a king who grew bored with life at court and decided to be a bard instead. Fflewddur carries a magical harp whose strings snap when Fflewddur exaggerates a little too wildly. (They break often.) It is not all bluster though, as Fflewddur actually is fairly Badass. His catchphrases are "A Fflam is (insert appropriate adjective here)!," and "Great Belin!"
Gwydion, Son of Don, is the war leader to High King Math and one of the most beloved and universally respected figures in all of Prydain. Taran idolizes him due to the many tales he has heard of Gwydion’s bravery and heroism, however, Gwydion takes no joy in his lifestyle, instead doing it to protect his people. He is very strong, brave, and wise, and leads his people in the battle against Arawn. He becomes something of a mentor to Taran.
The master of Caer Dallben and the mightiest enchanter in all of Prydain, Dallben is a steadfast ally of the Sons of Don and staunch opponent of Arawn. He is very old and wise, and serves as a mentor to the young Taran. He knows much of the happenings across Prydain, but rarely concerns himself with trivial matters, focusing all his attention on watching the movements of Annuvin. He possesses the mystical Book of Three, a tome of mysterious lore, which only he may read from.
All-Powerful Bystander: Despite being a powerful wizard and opponent to Arawn, Dallben rarely actually uses his powers to help the heroes. It is revealed that this is because Dallben is forbidden from killing.
A farmer who lives at Caer Dallben, Coll’s simple appearance belies his prowess as a warrior. In his youth, he marched into many battle, yet found that war was foolish and unfulfilling, and chose to become a farmer instead. He is the original owner of Hen Wen, although he knew nothing of her power until Dallben arrived. He now serves as Taran’s surrogate father figure, although when called upon to serve the Sons of Don, he does not hesitate to take up his sword once again.
Almighty Janitor: He’s a simple farmer, yet even Gwydion respects and defers to his experience.
Bald of Awesome: Taran is shocked to learn Coll was once a great hero, due to his lack of hair.
Badass Normal: He possesses no powers or enchantments or royal lineage, but he’s still one of the mightiest warriors in Prydain.
The oracular pig, Hen Wen, dwells at Caer Dallben, watched over and cared for by Taran and Coll. She does not possess the ability to speak, but may communicate her prophecies using special letter sticks. Due to her abilities she is greatly respected by Dallben and Gwydion, and Arawn himself once attempted to capture Hen Wen for his own uses.
Son of the chief bard, Taliesin, Adaon is one of the most respected bards in all of Prydain. A gifted seer, healer, and warrior, he accompanies Taran on his mission in The Black Cauldron, along with Prince Ellidyr, and serves as a mediator between the two.
The youngest son of Pen-Llarcau, Ellidyr is a bitter, scornful young prince who looks down on those beneath him in station. Due to his family’s diminishing reputation, he is eager to claim honor and restore his family’s name. He accompanies Taran on his mission in The Black Cauldron, along with Adaon, and becomes a rival to Taran.
Cool Horse: One of the hints that Ellidyr may not be as a big of a jerk as he seems is how loyal the otherwise-intractable Islimach is to him. To the point that when he dies, she jumps off the nearest cliff.
Darker and Edgier: Compared to Taran’s usual companions who are all unambiguously noble people, Ellidyr is a much darker and more complicated character.
The Prince of Mona, Rhun is foppish, clumsy, and generally clueless. He is, however, ultimately well-meaning and tries his best even though things never seem to work out for him. He accompanies Taran on his quest on the Isle of Mona.
Romantic False Lead: Rhun’s parents intend for Rhun and Eilonwy to be married, much to Taran’s chagrin. However, Rhun himself is not particularly interested and gladly steps aside when he realizes she’d be much happier with Taran.
Ugly Hero, Good-Looking Villain: Taran initially compares him unfavorably to Morgant due to his appearance. Morgant is handsome and well-spoken, but morally bankrupt, while Smoit is fat, unkempt, and loudmouthed, but incorruptible.
A member of the Fair Folk, and agent of King Eiddileg, sovereign of the Fair Folk. While he appears to be a thin and sickly creature, he's surprisingly adept at espionage and infiltration. Doesn't stop him from complaining about it though.
A gifted chemist and would-be con-artist; when the companions first encounter him, he'd accidentally managed to turn himself and his cat into giants. He's Brought Down to Normal and joins the companions on their final adventure, with mixed results.
The Eeyore: As a giant, Glew is miserable, morose, and perpetually unhappy.
For Science!: Very little is made of his motives for his experimenting with potions.
Grass Is Greener: As a giant, Glew was miserable and could only think of being small again. As a dwarf, he only wanted to be tall. Admittedly, his morose giant persona is very different from his prickly dwarf one.
Throw the Dog a Bone: In the end, it's agreed that he did ultimately help save the day, and he gets to join the Sons of Don on their trip to the Summer Lands.
A young shepherd from the Free Commots who convinces Taran to help defend his village from a group of bandits. He later joins Taran's group in order to guide them through the mountains of Annuvin to Arawn's fortress.
Arawn Death-Lord is the ruler of Annuvin, the Land of Death, and the Evil Overlord threatening Prydain’s stability. Unlike most Evil Overlords, Arawn is not a ruthless tyrant, but a cunning trickster who manipulates mortals through guile and deceit. Over time, he has stolen away most of Prydain’s greatest treasures and secrets, hording them in his fortress. He commands many terrible servants, including theGwythaints, theCauldron-Born, and the Huntsmen of Annuvin.
Orcus on His Throne: Arawn generally acts through proxies and rarely does anything on his own. This ends in Book 5, where it's shown that he can and will get his hands dirty when the reward justifies the risks. It also shows why he generally doesn't.
The vain, beautiful Queen Achren was once the ruler of all Prydain. Ages ago she was betrayed by her subordinate, Arawn, who became the new Evil Overlord. While she continues to serve Arawn, she is obsessed with finding a way to reclaim her former power and become ruler once again. Although not as powerful as she once was, Achren is still a formidable enchantress, and Gwydion fears her as much as he does Arawn.
Heel-Face Turn: Possibly; in the fifth book, it's unclear to what extent she's reformed, but she is nonetheless a valuable ally to the companions during their Enemy Mine.
Ninja Maid: She becomes Dallben's maid, for all intents and purposes after The Castle of Llyr, but The High King shows that though she's lost her magic, she's lost none of her cunning or physical prowess.
Woman Scorned: Her desire to get revenge on Arawn goes way past obsession…
The Horned King
Arawn’s mightiest war leader and the primary antagonist of The Book of Three and of the film version of the ''Black Cauldron,'' the Horned King is a bestial man who takes his name from the antlered mask he wears. No one knows his true name. Arawn has imbued him with great power, and he is charged with marshalling the Southern Cantrevs and leading an attack on Caer Dathyl.
One of the many kings of Prydain. He rides to Gwydion's war council at Caer Dallben and pledges his army in support of capturing the Black Cauldron from Arawn's clutches, but in truth he seeks the Cauldron for himself. He serves as the Big Bad of The Black Cauldron (the book, not the movie).
Black and Gray Morality: Gwydion uses his fall as an example to teach Taran how fine the line between good and evil truly is.
Deal with the Devil: Implied. It's indicated that he made a deal with Orddu, Orwen, and Orgoch to learn the secrets of the Black Cauldron (possibly to help the Sons of Don), and that the bargain cost him dearly.
A Wolf in Sheep's Clothing: More like a Wolf in Wolves' Clothing. It's immediately clear there's something wrong with Morgant when he arrives at the war council, but it goes unremarked upon until he confirms his Face-Heel Turn.
The Chief Steward of the House of Mona. He serves as a spy for and Dragon to Achren in The Castle of Llyr, and then to Arawn in The High King.
You Killed My Father: While he didn't explicitly kill Eilonwy's mother, he did sit back and let her die, then looted her corpse for the hell of it, which is where he found the amulet.
A wandering bandit and leader of a band of petty thugs who stalk the Free Commots. Like Achren, he is a recurring villain and comes the closest to inflicting real harm on the companions on several occasions.