To Kill a Kingdom is a YA romance fantasy novel written by Alexandra Christo and first published in 2018. It is a retelling of “The Little Mermaid” that reimagines the mermaid princess from Hans Christian Andersen’s story as a bloodthirsty siren whose kind has been engaged in a war against humanity for centuries. It follows Lira, the siren princess of the sea, who is tasked with taking the hearts of human princes each year for her birthday. When Lira makes a grave mistake, her mother, the Sea Queen, curses her to walk among the humans. Transformed into an ordinary human girl, she meets Prince Elian, a human prince and pirate whose sole mission is to rid the planet of sirens. Citations in this guide refer to the 2018 Feiwel and Friends edition of the novel.

Plot Summary

Lira, a young siren, is tasked with taking her younger cousin Khalia out to hunt for a heart for her birthday. They stalk a human ship, and when they are close enough, they begin to sing their hypnotic siren song, which will lure their human victims into the sea and to their deaths. Though Lira is still two weeks away from her birthday and therefore not supposed to steal a heart, she notices that there’s a prince aboard the ship. She only steals hearts from princes, and since the ship is the only vessel on which the Adekarosin prince sails, she decides to take his heart while her cousin takes the queen’s. When they return from their hunt, the Sea Queen isn’t happy and decides to punish them both—Lira for hunting too soon, and Khalia for not stopping her. Lira offers to take Khalia’s punishment to protect her from the Sea Queen’s wrath, and the Sea Queen beats her and crushes the heart she stole. The Sea Queen then tells Lira that she must hunt for the heart of a regular sailor for her birthday, taking away her glory as “The Prince’s Bane,” the siren known for killing only princes.

The Midasan Prince Elian sails on the pirate ship Saad with his loyal crew. He is a siren-hunting pirate, and his crew has just caught a siren. With his magic knife that sucks in the blood of those it kills, he kills the siren. The crew watches as she turns to sea-foam on the deck. Elian and his crew return to Midas, Elian’s homeland, where his parents and his sister Amara greet him with pride. The family throws a ball in his honor, hoping to persuade him to give up his adventurous life on his pirate ship in favor of preparing to one day become king.

Lira, embarrassed by the prospect of killing a common man instead of a prince, swims to the edge of the Diávolos sea to sulk. She is confronted by two mermaids who convince her to seek out the Golden Prince. The Midasan prince is known for killing sirens, and Lira thinks that the Sea Queen will be pleased with her if she brings her the prince’s heart for her birthday. She swims towards Midas to find him.

After hearing that the Princes’ Bane killed Prince Cristian, Elian’s friend and the Adekarosin prince, Elian goes to the Golden Goose, an outlaw’s pub, to find out any information that he can about her. A stranger tells him about the Crystal of Keto, which is hidden at the top of Cloud Mountain in Págos. He decides that his crew needs to get the Crystal to defeat the Sea Queen, but first he goes to find information about the Crystal in the royal library. When he finds nothing, his father tells him to stop looking for fairy tales. However, the suggestion makes him think to look at children’s books.

Lira swims to the shore of Midas and sees Prince Elian on the deck of the Saad. She starts to sing, but a mermaid who wants Elian for herself interrupts her. Lira and the mermaid fight, the commotion alerting Elian to their presence. Elian recognizes Lira as the Princes’ Bane, but the mermaid slams herself and Lira against the side of the ship, knocking him overboard. He crashes into the water, and the mermaid tries to drown him. Lira fights the mermaid off and kills her for trying to take Elian’s heart from her. Elian swims towards shore but has nearly drowned when Lira swims over to him. She nearly takes his heart, but he looks up at her just as the guards come to save him. She dives back into the ocean and swims away.

Elian wakes up in his room and goes to tell his crew that they are going to search for the Crystal of Keto. He returns to the Golden Goose to talk to Sakura, the mysterious pale woman who owns the pub. He confronts her about being the missing Págese princess, Yukiko, and he asks her for information about how to climb Cloud Mountain. She offers him the information in exchange for his hand in marriage. He agrees, so she tells him that the Crystal is at the top of the mountain in a special chamber that only a specific—and missing—necklace can open. She gives Elian a map that shows how to climb the mountain but declines to go with him.

The Sea Queen accuses Lira of killing a mermaid to protect a human prince. Lira tells her mother that she only wanted Elian’s heart for herself, which the Sea Queen takes as disobedience. As a punishment, the Sea Queen turns Lira human and challenges her to steal Elian’s heart without her song. Lira nearly drowns, but Elian and his crew spot Lira in the ocean, unconscious and naked, and rescue her. When she wakes, viciously attacking them and yelling at them in Psáriin, the language of the sea, they tie her up. They interrogate her, and Lira lies about her origin, telling just enough of the truth to be plausible. She watches them capture and kill a siren that she knows but doesn’t like. The crew doesn’t trust her, so they imprison her belowdecks.

The crew plans to abandon Lira in Eidýllio, where they dock so that Elian can strike a deal with the queen, Galina. Lira finds a lagoon and calls to her cousin Khalia. Khalia has a black eye and tells Lira that the Sea Queen punished her for letting Lira kill Prince Cristian. Lira realizes that her mother’s reign must come to an end, and Khalia agrees. Meanwhile, Elian meets with Queen Galina, who cannot touch men, or else they’ll become fully devoted to her. He makes a deal with her and leaves to find his crew when he realizes that Lira is still following him. She wants to continue on with the Saad. She warns Elian that if the Sea Queen gets the second Eye of Keto, she will become powerful enough to enslave the humans the way she enslaved the sirens, and she reminds him that she knows the ritual to get the Eye.

The crew returns to the Saad and continue on their journey. Madrid gives Lira a pirate makeover, making her feel like one of them for the first time. Later, the Sea Queen and her guard merman the Flesh-Eater visit Lira, using her stolen song to keep the crew asleep. She warns Lira that if she doesn’t steal the prince’s heart, she will steal Lira’s. Lira is conflicted over the idea of betraying the prince and feels betrayed that her mother used her own song against her. With the crew, she travels to Kléftes to find the Xaprár.

Elian has Lira pose as his new girl when they meet Tallis Rycroft, the ruthless captain of the Xaprár. His aim is to trick him while looking for the Págese necklace that is the key to the Cloud Mountain chamber. Rycroft invites Elian onto his ship, where Elian asks if Rycroft knows where to find a (fictional) stolen Midasan heirloom, hoping that the pirate will allow him to search his stash. Rycroft is one step ahead of the prince and reveals that the man who told Elian about the Crystal was part of the Xaprár crew. He tries to kidnap Elian to make him climb the Cloud Mountain, but Elian and Lira fight back. The Xaprár crew surround them, and Elian is knocked unconscious. Rycroft ties Lira and Elian up in a room belowdecks, and when Elian wakes up, he tries to escape. Soon, the crew of the Saad shoot cannonballs at the Xaprár, and one breaks the wooden pole to which Elian is tied. He manages to slip away from the pole, but with his hands still tied, he can’t help Lira. She tells him to go, and he reluctantly does.

When Rycroft finds Elian gone, he attacks Lira. She fights him relentlessly, scratching and biting him until he pins her against the wall. Pinned, she pulls his blade from his coat and stabs him through the abdomen. He falls, presumably dead. She retrieves the necklace from his neck as Elian, Kye, Madrid, and Torik come to rescue her. She is surprised to see that they came back for her, but before they can leave, Rycroft uses the last of his strength to shoot at Elian. Lira pushes him out of the way and is shot in the side. Elian catches her as she falls, pressing his hand against her wound to stop the bleeding. The medic on the Saad is able to save Lira, and the crew holds Rycroft prisoner, planning to turn him in when they get to Págos.

Once they reach Págos, they are greeted by King Kazue and his brothers. Elian is surprised to find Sakura, or Princess Yukiko, waiting for them as well. The king asks Elian to meet in private, so he goes with the royals to the great hall. The king acknowledges the deal that Elian made with Yukiko but wants a better deal: After Elian retrieves the Crystal, Págos will get the necklace, the Crystal, and the glory of having found it and defeated the Sea Queen. Elian agrees, more concerned with ending the war than receiving glory. The king also suggests that Elian and his crew take Yukiko up the mountain with them. Yukiko leads Elian, Lira, and the crew of the Saad up Cloud Mountain in freezing temperatures.

Elian and Lira sneak off together once the crew makes camp, and they watch the stars. Lira debates telling Elian the truth about being a siren, but she decides against it and instead asks him for a kiss, which he grants. Soon, the group arrives at the ice palace at the top of Cloud Mountain. They row across the moat on two small boats, and Yukiko leads them into the palace. They come to the chamber, which Yukiko opens using the necklace as a key. Inside, they find the Crystal of Keto suspended in perfectly blue, indestructible ice. Lira tells Elian that they need siren blood to free the Crystal, suggesting that his magic knife has siren blood in it from his siren kills. He stabs the knife into the ice, but it doesn’t work.

Lira later returns and cuts her hand, letting the blood drip on the ice and freeing the Crystal. She lied about needing siren blood and knew that the knife wouldn’t work. The only thing needed to free the Crystal was fresh blood. However, once she retrieves the Crystal, Yukiko confronts her, accusing her of being a siren. Lira admits it, explaining that the Sea Queen turned her human as punishment. Yukiko recognizes her as the Princes’ Bane, and Elian overhears. Lira tries to explain, but Elian immediately attacks her, angry at her deception and at himself for falling for it.

Elian and Lira fight, Yukiko encouraging Elian to kill Lira, but he can’t bring himself to hurt her. Instead, he lets her go, taking the Eye of Keto from her. Lira flees, and Yukiko scolds him for falling in love. Elian dismisses the prospect of marrying Yukiko and reveals that he’s made a deal with Queen Galina, who has agreed to marry Yukiko in his place. Yukiko reluctantly agrees, but only if Elian will agree to be the one to kill Lira.

Lira summons her mother, hoping to isolate the Sea Queen from her siren army so that she can use the Eye of Keto to kill the Sea Queen. She purposefully angers the Sea Queen so that she can get Elian to bring the Crystal out of the palace, but the Sea Queen uses her magic to summon a horde of sirens to the lake around the ice palace. The sirens engage in a bloody battle with the humans. Yukiko nearly kills Lira, but Khalia saves her and then tries to kill Yukiko. Elian, unfamiliar with Khalia, tries to kill her to save Yukiko, but Lira steps in, begging Elian not to kill her cousin.

Before they can reconcile, the Sea Queen attacks and turns Lira back into a siren. She commands Lira to steal Elian’s heart, and Lira pretends to lure Elian to the water. Elian, unaffected by her song, plays along. Lira kisses him and tells him that he’s not affected by her song because he’s stolen her heart. Elian decides to trust her and gives her the Crystal of Keto, giving Lira infinite power. As powerful as her mother, she now faces off with the Sea Queen, who tries to use her subjects against Lira and Elian. However, Lira convinces the sirens that they could be happier if they weren’t under the Sea Queen’s rule. The sirens turn to attack the Sea Queen, but she uses magic to separate them from the fight. The Sea Queen and Lira then battle until Lira uses all the magic she can muster to send two cyclones towards her mother, killing her. The force of the cyclones causes an avalanche, and Lira protects herself and Elian until it stops. When the rubble settles, Lira sees her mother’s lifeless body lying in the snow. In disbelief that it’s over, she and Elian watch as the Sea Queen’s body fades into sea-foam.

Some time later, Elian and the crew of the Saad return to the Diávolos Sea to see Lira, who is now the Sea Queen. Lira has opened up her kingdom to the world and given freedom to the sirens, who no longer hunt for human hearts. There is now peace between the sirens and the humans, and the sea kingdom is considered the 101st kingdom of the world. Lira transforms herself from her newly tentacled queen form into a human form and boards the Saad to visit Elian. They are still together and very much in love. As queen, she no longer has the time to travel with them, so Elian brings her stories of their adventures.