Conan and his companion, the thief Malak, are confronted by Queen Taramis of Shadizar. She tests their combat ability with several of her guards. Satisfied, she tells Conan that she has a quest for him. He refuses her, but when she promises to resurrect his lost love, Valeria, Conan agrees to the quest. He is to escort the Queen's niece, Princess Jehnna, a virgin, who is destined to restore the jeweled horn of the dreaming god Dagoth; a magic gem must first be retrieved that will locate the horn. Conan and Malak are joined by Bombaata, the captain of Taramis's guard. Bombaata has secret orders to kill Conan once the gem is obtained.
The gem is secured in the fortress of a powerful wizard, so Conan seeks the help of his friend, Akiro, the Wizard of the Mounds. Akiro has been captured by a tribe of cannibals, and must first be rescued. The adventurers encounter Zula, a powerful bandit warrior being tortured by vengeful villagers. Freeing Zula at Jehnna's request, Conan accepts the indebted warrior's offer to join their quest.
The adventurers travel to the castle of Thoth-Amon, where the gem is located. As they sleep by the lake surrounding the castle, the wizard takes the form of a giant bird and kidnaps Jehnna. In the morning Akiro divines this and also divines a hidden entrance to the castle through a water gate. As they search for Jehnna Conan is separated from the group, and the others are forced to watch him battle a fierce man-beast in a hall of mirrors. By breaking the mirrors Conan mortally wounds the creature which is revealed as a polymorphed Thoth-Amon. With the wizard's death, the castle begins to disintegrate, forcing the group's hasty retreat. They are ambushed by Taramis's guards, but drive them off. Bombaata feigns ignorance about the attack. The gem reveals the location of the jeweled horn. Jehnna expresses romantic interest in Conan, but he rebuffs her and declares his devotion to Valeria.
They reach an ancient temple, where the horn is secured. Jehnna obtains it while Akiro deciphers engravings. He learns that Jehnna will be ritually sacrificed to awaken Dagoth. They are attacked by the priests who guard the horn. A secret exit is revealed, but Bombaata blocks the others' escape and seizes Jehnna. Despite this treachery, Conan and his allies escape from the priests and trek to Shadizar to rescue Jehnna.
Malak shows them a secret route to the throne room. Conan confronts Bombaata and kills him in combat. Zula impales the Grand Vizier before he can sacrifice Jehnna. The rising Dagoth becomes distorted from a human statue into a monstrous entity. He kills Taramis, then attacks Conan. Zula and Malak join the fight, but are effortlessly swept aside by him. Grappling with the monster, Conan tears out Dagoth's horn, weakening Dagoth enough to kill him.
The newly crowned Queen Jehnna offers each of her companions a place in her new court: Zula will be the new captain of the guard, Akiro the queen's advisor, and Malak the court jester. Jehnna offers Conan marriage and the opportunity to rule the kingdom with her, but he declines and departs to find further adventures and his own place in the world.
Arnold Schwarzenegger as Conan
Grace Jones as Zula
Wilt Chamberlain as Bombaata
Mako as Akiro
Tracey Walter as Malak
Sarah Douglas as Queen Taramis
Olivia d'Abo as Princess Jehnna
Pat Roach as Thoth-Amon
Jeff Corey as Grand Vizier
Sven-Ole Thorsen as Togra
André the Giant as the Dagoth monster (uncredited)
Ferdy Mayne as The Leader
Based on the character Conan the Barbarian created by Robert E. Howard
the sequel to Conan the Barbarian (1982)