Conan has been leading a band of kozaks for some time, and it's causing no end of problems for the local Turanian governor Agha. Noting Conan's predilection towards Damsels in Distress, he decides to use his most beautiful slave, Octavia, as bait to lure Conan into a trap. Octavia, looking to escape her enslavement, warns Conan of the attack, and the two flee to a deserted island in the middle of a lake. Unfortunately, this was the governor's plan all along, and with his best men he follows them.
On the island, Conan and Octavia are shocked to find a city that wasn't there the day before, full of hanging tapestries, golden banquet halls, and beautiful sleeping people. Heading for the center of the city, they find it's keeper, Khostral Khel, a millennia old Humanoid Abomination who has just awoken from his long slumber, who has brought the city back to it's former glory.
Trapped and with nowhere to run, Conan and Octavia must contend with a giant serpent, Agha's forces, and the living horror that is the devil in iron.
- Action Prologue: The fisherman breaking into the temple.
- As You Know: Ghaznavi, a Turanian counselor, tells Jehungir, a Turanian noble, of the island on which most of the action takes place, and how they lost a detachment of troops near it to Conan's kozaks. Lampshaded when Jehungir wryly replies "I am not likely to forget that."
- The Bait: Octavia, intended to so enrapture Conan that he'll come alone to an island on the rumor she'd escaped and awaits him there.
- Barbarian Tribe: The kozaks, made up of criminals, deserters, and other undesirables, who've formed their own society. Conan is leading them.
- Bedsheet Ladder: How Octavia escapes her captivity for true. Though again, with torn tapestries instead of proper bedsheets.
- Blue Blood: Octavia was a Nemedian noble before she was Made a Slave.
- Cold-Blooded Torture: Jehungir has a Shemite torturer, and just the threat of being turned over to him for an evening is enough to make Octavia's resistance to her part in the plan vanish. Octavia is then handed to Jelal Khan, "a nobleman whose name was a byword for degeneracy." We're not told what either of them did to or planned for the girl, but it's enough to prompt her to escape.
- Curiosity Is a Crapshoot: The fisherman rouses the evil by his curiosity.
- Damsel in Distress: Octavia.
- Darkness = Death: Literally. Khosatral's necromancy only fully revives the population of Dagon at night, "which is akin to death," as they've been dead to long to be fully restored to true life. By day, they fall into a deathlike slumber.
- Deadly Decadent Court: The city that appears; what Octavia fled.
- Eldritch Abomination: Khosatral Khel, first appearing as an Evil Sorcerer and a Necromancer, turns out to be this when Conan kills him, reverting to a form so ghastly that it causes Conan to flee in fear. In fact, he's stated to be this, as he came from the primordial chaos. The name of the country he's ruled? Dagon.
- Humanoid Abomination: Khosatral Khel, again, as he has taken a human form. His description is a quote for this very trope!
- Faux Death: Conan finds people rousing from it.
- Femme Fatale: Octavia was ordered into it.
- Golem: Khosatral Khel is basically one, an Eldritch Abomination who made an iron body for himself because no mortal flesh could properly serve as a vessel for his mighty essence.
- Human Sacrifice: In the back story.
- Intro-Only Point of View: The fisherman dies and so exits the story.
- Lotus-Eater Machine: Conan at first assumes the city is this, due to the drugged, sleepy behaviour of the inhabitants. Subverted: the townspeople act that way because they are brought back after centuries of death, and Khosatral Khel expends immense amounts of power keeping their mental faculties working.
- Made a Slave: Octavia's Backstory.
- Made of Iron: The villain, literally, making him nearly invulnerable, to everything except the dagger.
- Mercy Kill: Octavia begs for this when she and Conan are cornered by the apparently invulnerable Khosatral Khel (apparently Khosatral has threatened her with a Fate Worse than Death). Conan instead tells her that he will hold off Khosatral for as long as possible to give her a chance to escape the island.
- Necromancer: Who roused the city.
- Neutral Female: Octavia doesn't even try to help out while Conan is fighting the giant snake.
- Oh, Crap!: When Khosatral sees that Conan has the magic dagger, he seriously reconsiders his attempt to murder our favorite Cimmerian.
- Rescue Sex: Conan is surprised that Octavia rejects this and has to seduce her.
- Sealed Evil in a Can: The Necromancer, until awakened by a fisherman stealing the dagger that was keeping him inert.
- Snakes Are Sinister: A forty-foot snake is one of the creatures doing Khosatral Khel's bidding.
- Temple of Doom: Where the trouble was unleashed.
- This Was His True Form: A rare inversion. While Khosatral was human in his life as an Evil Sorcerer, when he died, he reverted into something so ghastly that it sent Conan himself fleeing in fear.
- Thunderbolt Iron: Enabled a slave revolt.
- Wait Here: Conan tries this on Octavia, warning her to stay outside a room with a gaunt snake while tries to sneak past it and get the magic knife. She doesn't listen, Hilarity Ensues.