May contain plot details
|“||If you are the sickness, I suppose you can't also be the cure.||”|
– Cardan Greenbriar, The Wicked King
Cardan has curly, iridescent, midnight hair and sharp cheekbones. He has long eyelashes. His eyes are described as black with a golden ring around the pupils. He usually wears kohl under his eyes. Cardan is said to be lean and tall, with very pale skin. He has a number of scars on his back from his abusive eldest brother, Prince Balekin. Cardan possesses a slim, nearly hairless tail with a tuft of black fur at the tip which is often kept tucked away in the back of his shirt. He is described as more beautiful than the rest of the Folk by Jude.
He is almost always seen wearing extravagant clothes made of rich fabrics, studded with gemstones and exotic feathers and patterns. He wears a circlet of gold. In the official art of the characters in How the King of Elfhame Learned to Hate Stories Cardan is depicted as a tall figure with very pale skin, long black hair, and black eyes.
Prince Cardan is cruel, sarcastic, prideful, and manipulative. He is described as not being any good with a sword and doesn't show any interest in the crown. According to him, his redeeming quality is that he is no murderer. Often, he struggles to understand his emotions and tries to keep up a mask to his true emotions by displaying sneers and sarcastic remarks. Even with his masks, he occasionally shows a softer side along with fear, shame, desire, and even care. When he's nervous he often smiles. Cardan is known for his charming and witty abilities which allow him to slyly escape danger and trouble. However Cardan has shown that he does feel love. He had just never truly learned how to do so. He is also a sweet talker and can talk almost anyone into anything. He knows how to charm a crowd and how to entertain. Jude also mentions that his glamour is more powerful and seductive than other Folk. As a prince of Faerie, no matter what he wants, he knows what's expected of him. Cardan is very good at playing the fool to disguise his own cleverness.
Cardan was deemed to be a harbinger of ill luck after his birth by the Royal Astrologer, Baphen.
Cardan's mother, Lady Asha, found children to be irritating, and thus neglects Cardan. In an enchanted globe Jude finds in Eldred's desk, she sees Cardan as a very small child. He's dressed in a shirt that's too large and hangs down like a gown. He is barefoot and his feet and shirt are streaked with mud. He wears dangling hoops in his ears, as though an adult gave him their earrings. Jude sees him try to get his mother's attention, only to be rebuffed. He storms off and picks a fight with an older boy. At the sound of the shuffle, Asha turns and laughs, clearly delighted by his escapade. This makes Cardan smile.Cardan was left to be suckled by a little black cat whose kittens came stillborn. After his mother was sent to the Tower of Forgetting, Cardan was sent to Balekin's estate. Cardan was dressed in rags and looked to his mother for approval, which came only when he was awful. He was an abandoned prince, weaned on cat milk and cruelty, left to roam the palace like a little ghost. Then he was forced to endure his brother enchanting mortal into beating him for poor swordsmanship.
Cardan never felt any love from his many brothers and sisters. His father, the late High King, has not shown much interest in his youngest child, disregarding Cardan. His brother, Prince Dain, played a trick on Cardan that resulted in the Court thinking Cardan had killed the beloved mortal of Val Moren. Dain saw to it that though Cardan protested, no one would hear his side of events. Dain told the story of the youngest prince's recklessness and arrogance. The High King would not even allow Cardan an audience. "And so Prince Cardan's reputation was made, he had little to do but further it." He is then forced to reside with his eldest brother, Prince Balekin, in Hollow Hall, enduring Balekin’s harsh punishments and cruelty.
Cardan attends the revel at Court with his inner circle, Nicasia, Locke, and Valerian. Jude and Taryn witness Prince Cardan and his friends' cruelness in tearing the wings of a disrespectful faerie. Jude fears what would happen if Cardan ever becomes king.
At their lessons the next day, Cardan kicks dirt onto Jude and Taryn’s food. He threatens to ensorcell Jude into eating the dirt. He tells Jude she doesn't belong in the Summer Tournament because it's not for mortals. He tells her to withdraw, or she will wish she had.
The following day, Jude sneakily puts salt in Cardan and his group's lunch in retaliation for kicking dirt on her lunch yesterday. After lessons they attack Jude and Taryn, throwing them in the river. Cardan tells Jude to quit attending lessons with them and to abandon the Summer Tournament. He wants here to tell Madoc that she doesn't belong with them, her betters. If she agrees to do this, he will save her from the nixies in the river. When Jude refuses, Cardan tells Taryn that if she kisses him on both cheeks and doesn't defend Jude by "word or deed," he won't hold her accountable for Jude's defiance. To get the protection, she must leave Jude to drown in the river. Jude tells her to do it and that she'll be fine, but is still hurt when Taryn does it. Cardan continues to threaten Jude. He tells her that they will break her because she is mortal and fragile and that she should give up. Jude tells him she never will.
At lessons the next day, he is seen talking to a crying Taryn, and Jude slams him against a tree and warns him to stay away from Taryn. Cardan is shocked but plans to get revenge. At the Summer Tournament's mock war, Jude fights mildly at first but after provocation from Cardan, who is on the other team, she fights with viciousness against him and wins the Tournament for her side. After the Tournament, Cardan demands her submission, but Jude does not give in. Instead she tells him that she will shame him with her defiance, and that while he might win in the end, she will make sure to take everything she can away from him on the way down. Cardan is left speechless and she goes away unscathed.
At the next day of lessons, Valerian forces Jude to eat faerie fruit and begins choking her with it. Cardan shoves Valerian off her saying that if she dies, his prank will be over before it begins. The faeries begin making Jude embarrass herself. Cardan tells Jude to kiss his foot and tell him how much she admires him. Before she can, Locke intervenes and tells him he is taking her home. Cardan stabs her finger making her bleed, as she sucks on her finger, Jude realizes the salt in her blood is stopping the effects of the faerie fruit.
While spying for Prince Dain at Hollow Hall, Jude witnesses Balekin emotionally and physically abusing Cardan. Balekin forces Cardan to demonstrate his skills with a sword. When he easily overpowers him, Balekin tells him he is weak and has a human servant begin beating him with a belt. Cardan grabs the sword and Balekin tells him to go ahead and kill the human. Cardan replies that he is not a murderer. Jude realizes that Cardan has been raised and instructed on cruelty.
Cardan attends the party at Locke's estate. Jude sees he is drunk and has two female faeries all over him. He can't stop staring at her.
At the coronation Cardan steps between Jude and Locke while they're dancing. He chides Locke for playing around with Jude and Taryn, but at that time Jude does not understand his meaning. When the ceremony starts, the entire royal family stands behind the throne except for Cardan, who is nowhere to be seen. Eldred, the High King, gives up the power of the crown and prepares to crown Dain. However, Balekin stages his coup with the support of Madoc. Balekin kills Princess Elowyn and Madoc kills Dain. Balekin beheads Taniot and runs his sword through Eldred. The High King can only be crowned by someone of Greenbriar blood, so Balekin turns to his two remaining sisters and tells them to crown him. Princess Caelia is willing to do it in order to stop the bloodshed, but is shot with a bolt from the Ghost. Princess Rhyia kills herself rather than make Balekin High King. Balekin is given three days to become High King by Lord Roiben, or the courts will leave without pledging loyalty to the crown.
The revel continue as if the slaughter did not happen. To her luck, Jude encounters a drunk Cardan under the long banquet tables. He reveals to her that his father despised him. She lets him lead her up to the palace floors before threatening him with a dagger. She forces him to come into the lair of the Court of Shadows and ties him to a chair. The Roach and the Ghost arrive, and with a prompt from Cardan, the Ghost admits that he was the one who poisoned Liriope with orders from Dain, because there was a prophecy saying if the child of Liriope was born, Dain would never be king. It was known that the child Liriope was carrying had been sired by Dain. She leaves Cardan in the Ghost and the Roach's care while she returns to Madoc's estate.
Jude returns to the Court of Shadows and interrogates Cardan. When she asks him why he hates her so much he avoids the question, until Jude threatens to shoot him with a crossbow. He tells her that he envies her because Madoc loves her despite her being his step-daughter when Cardan’s own father despised him. He also envies her because she doesn’t have an abusive older brother. Another reason for his hate is because he believed that she stole Locke from Nicasia, making her cry.
Jude asks him about the piece of paper she found on which he wrote her name over and over again with such intense hatred, but he hesitates to answer. After a little more pressing from Jude, he then admits that he is attracted to Jude and thinks about her often and hates himself for wanting a mortal. Jude then kisses him and he kisses her back.
Cardan proposes a bargain where Jude will tell Balekin that Cardan will crown him, and in return, Balekin shall give Cardan lands and gold and give to Jude whatever she wants. They form a sort of friendship. He tells her he does not want to be the High King. Jude ponders her options and decides on what she will do. On the third day after the royal massacre, Balekin is going to host a feast at Hollow Hall. With the courts gathered at the feast, someone of Greenbriar blood will have to be crowned before the courts leave without swearing fealty.
Jude tells the tale of how Oak came to be of Greenbriar blood to the Court of Shadows and Cardan. She tricks them into thinking that she is going to make Cardan crown Oak, then whisk the young boy to the mortal world where he'll grow up without faerie cruelties. She persuades Cardan to swear himself into her service because she tells him she cannot trust him with the crown of Faerie in his hands. Cardan pledges himself grudgingly, giving Jude the power to command him to do anything she wishes and which he cannot refuse, but only for a year and a day.
Cardan helps Jude find allies amongst the different Courts to support her plan. She convinces Severin, son of the Alderking, and with Lord Roiben, the ruler of the Court of Termites.
At the feast at Hollow Hall, Jude walks in on Cardan’s arm, shocking everyone present. Balekin does not immediately seize Cardan as he now knows the importance of a willing participant in a coronation. Jude lures Madoc to a secluded hallway and they fight.
Jude then joins Cardan at the dinner table and gets ready for the explosion the Bomb is about to create. When it happens, the Roach shoots bolts at Balekin to distract his guards while the Ghost steals the Crown of Faerie amidst the chaos. The Ghost mistakes Taryn for Jude and throws the crown to her. Jude wrestles the crown from Taryn and gives it to Oak. Jude tells Cardan to show Oak what he should do as the one being crowned, and Cardan kneels, beckoning Oak to do the same. However, Jude commands Cardan to stay completely still in his kneeling position. Oak performs the coronation ceremony and places the crown on Cardan’s head, as he practiced with Vivi, and Cardan becomes the new High King.
Now Jude has absolute control over the most powerful being in Faerie for a year and a day. Cardan is furious at her betrayal, as he does not want to be High King. Oak is sent to live with Vivi and her girlfriend Heather in the mortal world. Cardan appoints Jude as his seneschal while also telling her that he has not yet forgiven her.Grimsen, who is in exile. He comes to Cardan to ask to have his exile lifted. Cardan grants him that on the condition that he will show Cardan his loyalty in his deeds, rather than with his words.
Then Mother Marrow comes forward, and gifts Cardan a piece fabric woven of spidersilk and nightmares. She tries to trick Cardan into a geas, but is stopped by Jude. Jude is informed that Balekin wishes to speak with Cardan and goes to meet him herself. She meets Cardan’s mother Lady Asha in the Tower of Forgetting.
She comes back to find that an attempt was made on Cardan’s life while he was drunk and in bed with another faerie. He got away safely but has a wound. Jude moves him to her bedroom while she inspects his room and in his drunken state, he tells her to kiss him over and over again until he is sick of it. He falls asleep before Jude can reply. Jude finds out that Nicasia shot at Cardan out of jealousy, but her target wasn’t Cardan but the other girl with him.
Jude tells Cardan about Balekin’s wish to meet with him but Cardan refuses his demands. They find out that Balekin is working with Queen Orlagh of the Undersea. Jude tells Cardan to seduce Nicasia to find out more about Queen Orlagh’s plan. Cardan uses his seductive talents on Jude instead and they end up kissing. They end up in bed together. Jude later reveals they did not go all the way. Cardan finds out from Nicasia that Queen Orlagh is planning to rebel against him and they soon receive a warning. They think that the Undersea plans to hurt Oak, who is coming to Elfhame for Taryn and Locke’s wedding and take appropriate precautions. But the Undersea abducts Jude instead.
Cardan does everything he can to get Jude back. He agrees to all of the Undersea’s terms, even letting them attack his kingdom without retaliating. After Jude returns, she finds out that Cardan and Madoc blamed each other for her abduction.
Later, when she goes to palace, Cardan takes her into his bed and confess some of his feelings, making Jude speechless.
Cardan is first seen when Jude comes in the court as Taryn. Cardan asks questions and then tells her to come to his room. There, he tells that her that he knows she is Jude and asks why she has not answered any of the letters he sent her. He tells her the exile was a trick.
Madoc attacks and takes Jude. While she is planning her escape, Cardan comes to save her with the Roach.
Cardan and Balekin have a bad relationship because Balekin is abusive toward Cardan, both physically and emotionally. Balekin believes Cardan is too weak. Balekin forces Cardan to spar with him, taunting and mocking him thee entire time. Afterwards, Balekin has a human servant beat Cardan with a belt and tells him that he is "punishing him because he loves him." However, Balekin was the only sibling of Cardan's who took him in when Dain got him kicked out of the palace.
Though Lady Asha was his mother, she ignored Cardan as a child but enjoyed the higher status he gave her. She only paid him attention when he got into fights as it amused her. When she is released from the Tower of Forgetting, Cardan allows her to return to the High Court, saying that he supposes he has some fondness for her yet.
Locke is part of Cardan's inner circle. However, their friendship hit a rough patch when Locke stole Nicasia from Cardan. Their relationship remains rocky while Locke is involved with Jude because of Cardan’s suppressed feelings for her.
Main article: Cardan and JudeEvery time Jude thinks of Cardan she feels two things: hatred and rage. She hates him for being a spoiled prince, for bothering and threatening her sister, and for being so self-centered. She knows Cardan's hatred for her is deep, and he shows it in each one of his actions towards her. After the coronation, when Jude takes Cardan as her prisoner, he admits that his hatred for her is caused by jealousy and envy of the way Madoc loves her while his own father doesn't and that her siblings love her while his do not. After a little more pushing from Jude, Cardan admits he desires her, and how he loathes himself for feeling that way. Cardan admits that he thinks about her often and as retaliation Jude kisses him and he kisses her back. After that, Jude and Cardan’s relationship becomes stressed as they are obviously involved with each other, but neither of them admits to feeling anything other than a passing desire for each other.Cardan tells Jude that her exile was only a trick that was meant to prevent war and also to establish himself as a respectful ruler. He continues explaining that his true intention was for her to come back and he then notes upon the fact that Jude had tricked many people in the past and was sure she would notice his careful wording. He then told Jude that he sent her multiple letters to ensure her return home. Although the two don't make peace with each other immediately, they both show mutual affection and longing towards each other. Cardan admits he's been in love with her for a long time, Jude doesn't know how to respond. After Cardan is free from the curse, Jude tells him that she is in love with him and they end up ruling Elfhame as the High Queen and King.
Nicasia and Cardan were lovers before she left him for Locke. Locke seduced Nicasia away from Cardan, but after Locke left her to court Taryn, she wanted Cardan again. She feels jealousy towards all those who have Cardan's attention, as shown when she tried to shoot bolts at a girl in the bedroom with Cardan. Cardan tells Jude that he loved Nicasia and says that she is magnificent. Nicasia really did love him, and because she betrayed Cardan with Locke she is terrified he will never her again. Cardan is unable to forgive Nicasia for her betrayal.
- Cardan is about a year and a half older than Jude. 
- Jude receives a beautiful dress for the coronation, which she thinks is from Prince Dain, but Cardan was the one who gave it to her.
- While living at Hollow Hall, Cardan used to help mortals escape back into the mortal world.
- The prophecy from his birth stated, "He will be destruction of the crown and the ruination of the throne. Only out of his spilled blood can a great ruler rise." 
- Jude remarks that Cardan smells like moss, oakwood, and leather.
- Cardan has been learning how to pick pockets from the Roach.
- "I think about you. Often. It's disgusting, and I can't stop."
- "Time to change partners. Oh, did I steal your line?"
- "I am no murderer."
- "How has the night been going for you? Mine has been full of dull conversations about how my head is going to find itself on a spike."
- "Have I told you how hideous you look tonight?"
- "Locke hasn't gotten around to seducing me yet, if that's what you're asking. I suppose I should be insulted."