During medieval times, Galen apprentices with Ulrich, an elderly sorcerer who is the last of his kind. When villagers from Urland, led by teenager Valerian, arrive at Ulrich’s home, the sorcerer has a vision of his own death. The villagers want him to use his magic to destroy a dragon. They explain that their king made a pact to hold a lottery twice a year to select a virgin to be sacrificed to a fire-breathing dragon, in return for it leaving their houses and crops unburned. As Ulrich agrees to help, the king’s soldiers arrive and their leader, Tyrian, demands proof of Ulrich’s powers. Ulrich hands his magic amulet to Galen, asking him to place it in its box and retrieve Ulrich’s dagger. Galen finds the dagger and drops it from a tower window, but before he can rejoin his master, the doors and windows suddenly shut, locking him inside. Ulrich recites an incantation over the dagger, but the moment he hands it to Tyrian, the soldier stabs him. As Ulrich dies, the tower doors fly open and free Galen. Later, Galen lights Ulrich’s funeral pyre and the flames burn green. The next day, Ulrich’s manservant, Hodge, gathers Ulrich’s ashes in a pouch. Galen takes ownership of the sorcerer’s magic amulet and pledges to fulfill Ulrich’s promise to slay the dragon, despite being merely an apprentice. When he and Hodge go to the villagers’ campsite, Galen declares himself to be their new sorcerer. Meanwhile, in Urland, a sacrificial virgin is led up the mountain and chained outside the entrance to the dragon’s cave. Villagers leave, and the girl attempts to escape, but she is burned to death by the dragon’s fiery breath. The next morning at the camp, Valerian awakens early to bathe in a nearby stream. Galen jumps in the water before Valerian can stop him, and discovers that Valerian is female. She confesses that her parents disguised her as a boy since birth to protect her from the lottery. She also reveals that the princess and daughters of rich villagers are exempt. Galen has a vision of Tyrian attacking the campsite, and runs back to find Hodge mortally wounded. Before he dies, the servant hands Ulrich’s ashes to Galen, and tells him to throw them in the burning lake. Later, Galen asks Valerian to lead him to the dragon’s cave. Just inside, he finds bones and fallen dragon scales. Suddenly the earth shakes, indicating the dragon’s presence. Galen steps outside, holds up his amulet, and recites a spell. As the amulet glows, an avalanche buries the cave entrance. That night, villagers celebrate Galen’s victory in Urland. Valerian wears a dress and looks feminine, stunning villagers who have always known her as a male. The celebration is interrupted by Tyrian and his men, who are under orders to take Galen to King Casiodorus Rex. The king declares that Galen did not have permission to cast the landslide spell. He explains that his older brother once assembled his best fighters to attack the dragon, but they disappeared, and the dragon’s reprisals against the kingdom were brutal. That is why Casiodorus Rex negotiated a pact with the dragon, sacrificing a few virgins to save the majority. Galen declares he killed the dragon, but the king doubts him and takes the amulet. Locked in a cell, Galen tries to escape by using incantations, but they are ineffective. Princess Elspeth visits and asks him to understand that her father is protecting their people. When Galen reveals that she has been spared from the lottery because of her social position, Elspeth does not believe him. However, she asks her father for the truth, and he admits he protected her from the lottery. Suddenly, an earthquake erupts as the dragon bursts free from the mountain. Elspeth runs to Galen’s cell and frees him. Stealing a horse, he rides to Urland and sees the dragon flying above, burning the village with his fiery breath. Later, Tyrian and his solders search the smoldering ruins for Galen, but find no sign of him. Tyrian declares the king is holding a new lottery, and Valerian must participate. After Tyrian departs, Galen comes out of his hiding place. Valerian’s blacksmith father takes him and Valerian to a nearby stream to retrieve the “dragonslayer,” a spear he forged but never had the courage to wield. Valerian worries that it will not be effective against a dragon, and Galen agrees he needs the amulet to enhance the weapon’s power. During the lottery, Galen sneaks into the king’s quarters and searches for the amulet. Meanwhile, Valerian stands with the other virgins as the priest picks a name. The king is stunned to learn it is Princess Elspeth, and insists the priest misread the name. He demands another name be chosen, but that slip also reads “Princess Elspeth.” Elspeth steps forward and admits that, having learned her name was kept out of previous lotteries, she made up for the injustice by substituting her name for everyone else’s. Her father wants to declare the lottery invalid, but she refuses, and Tyrian tells the king he cannot help him. The king discovers Galen searching for the amulet, and professes a newfound appreciation for the apprentice’s skills. Giving Galen the amulet, he begs him to help Princess Elspeth. Galen takes the amulet to the blacksmith’s shop to empower the dragonslayer spear. Meanwhile, Valerian sneaks to the dragon’s lair to gather fallen dragon scales, but she discovers a baby dragon and quickly leaves. Later, she surprises Galen with a shield she made from dragon scales. She worries he will die, and believes he is acting out of love for the princess. Galen dispels Valerian’s fears by admitting he loves her, and they kiss. At the dragon’s lair, soldiers chain Princess Elspeth to the sacrificial post. When Galen arrives, Tyrian threatens to kill him for interfering, but Galen cuts Elspeth’s chains with his spear. However, as Galen and Tyrian fight, Elspeth enters the dragon’s cave instead of running to save herself. As Elspeth screams inside, Galen kills Tyrian with the dragonslayer spear and rushes into the cave. He finds three little dragon’s feeding on Elspeth’s body, and kills them. Deeper in the cave, he finds the dragon in a lake of burning water. It breathes fire at Galen, but Valerian’s shield protects him. He runs back through the cave and hides on an outcropping above Elspeth’s body, and when the dragon stops upon seeing the dead dragon babies surrounding her, Galen jumps on its back. When he rams the spear into the dragon’s neck, it breaks in half. Galen grabs his shield for protection and escapes. In the morning, he tells Valerian the dragon is still alive. She wants them to leave together, and her father agrees it would be best. Noticing a strange planetary line-up above the mountain, Galen has a vision of burning water, and remembers Hodge’s instructions. Galen explains that Ulrich realized he was not strong enough to make the journey to Urland, so he planned his cremation so that Galen could carry his ashes. Galen and Valerian rush to the burning lake in the dragon’s cave, where Galen dumps Ulrich’s ashes into the water. The amulet glows green as Ulrich rises from the water and reunites with his apprentice. Ulrich instructs Galen to destroy the amulet at the right moment. The sorcerer vanishes, but reappears at the top of the mountain as the planets align. Ulrich allows the dragon to capture him, then calls to Galen to smash the glowing amulet. Ulrich explodes, killing the dragon, and it falls from the sky. Later, as Galen, Valerian, and villagers surround the dragon’s carcass, the king is declared the “Dragonslayer.” As Galen and Valerian leave town, he admits he misses Ulrich and the amulet. Valerian claims not to mind that Galen is not a sorcerer. However, he wishes they had a horse, and one appears as if by magic.