While praying at an altar with his traveling companion and fellow thief Malak (Tracey Walter), Conan (Arnold Schwarzenegger) is confronted by Queen Taramis (Sarah Douglas) of Shadazar, who tests the pair in combat with several of her guards attempting to capture him. She tells him that she has a quest for him, which he initially refuses. The queen uses her power to learn his greatest desire, to resurrect his beloved Valeria, and promises to bring her back to him, to which Conan agrees to the quest. They learn that the queen's niece, Jehnna (Olivia d'Abo) has been destined, due to a special birthmark, to find a special jewel that only she can touch and with it obtain the jewelled horn of the dreaming god, Dagoth. She tasks Conan and Malak to protect her on this journey, while her captain of the guard, Bombaata (Wilt Chamberlain), is secretly asked to betray and kill Conan once the task is complete so they can sacrifice Jehnna to the god without interruption.Due to the task of confronting a powerful wizard for the gem, Conan seeks the help of his friend, another wizard named Akiro (Mako) whom he saved from a tribe of cannibals that were about to eat him to absorb his magic power. Enroute they also meet Zula (Grace Jones), a powerful warrior and a bandit whom Jehnna and Conan save from being tortured by a group of villagers she and other bandits tried to raid, she joins the quest indebted to Conan for saving her life. They find their way to the wizard Toth-Amon's (Pat Roach) icy castle upon a lake. When they camp, however, the wizard transforms into a bird of smoke and takes Jehnna during the night. The travelers make their way into the castle and Conan is able to defeat the wizard, destroying the illusion and prompting a hasty escape from the castle. With the jewel now in hand they start to make their way to where the horn is hidden. Jehnna expresses interest in Conan, but he drunkenly rejects her for Valeria. They make their way to an ancient temple, and using the power of the jewel Jehnna is able to find and obtain the horn. Guardians of the horn attack the group and they manage to slip out a back entrance. Bombaata, having failed previously to kill Conan instead blocks their exit and takes Jehnna. After the others escape they make their way back to Shadizar and find their way inside due to a secret route Malak's "cousin's sister's brother" used previously to escape captivity. They confront Bombaata and Conan beats him in combat, killing him. Meanwhile, Jehnna is prepared to be sacrificed and the horn is placed upon the head of the Dagoth statue. Upon its first signs of life, they attempt to sacrifice Jehnna, but Zula intervenes and kills the Grand Vizier (Jeff Corey) first. Having received an improper sacrifice, the statue becomes angry and begins to twist and distort into the demonic of version Dagoth (André the Giant). Queen Taramis is killed and Conan battles the Dagoth, eventually killing it by removing the horn from its head.After the battle, the newly crowned queen Jehnna offers each of her companions a place in her new court. Zula becomes the new captain of the guard, because Jehnna does not see any reason why a woman can't do as good a job as any man. Akiro becomes her new wiseman and advisor, and Malak steps forward and nearly trips, qualifying him for the position of court fool. She offers Conan her hand and the opportunity to rule the kingdom together, which he declines; having been promised a kingdom already, and departs on his own for further adventures and to find his own place in the world.