"Red Nails" is the last of the stories about Conan the Cimmerian written by American author Robert E. Howard. A novella, it was originally serialized in Weird Tales magazine from July to October 1936.
It is set in the pseudo-historical Hyborian Age and concerns Conan encountering a lost city in which the degenerate inhabitants are proactively resigned to their own destruction. Due to its grim themes of decay and death, the story is considered a classic of Conan lore and is often cited by Howard scholars as one of his best tales.
"Techotl pointed to a black column of ebony which stood behind the dais. Hundreds of red dots scarred its polished surface — the bright scarlet heads of heavy copper nails driven into the black wood. "Five red nails for five Xotalanca lives!" exulted Techotl, and the horrible exultation in the faces of the listeners made them inhuman..."
- Robert E. Howard, "Red Nails"
"Red Nails" begins in the jungles far to the south of any known civilized or barbarian lands. Valeria of the Red Brotherhood enters this wilderness, fleeing persecution after killing a would-be rapist. She is followed into the wilderness by Conan, a fellow adventurer who hopes to make her his woman. They meet and quarrel, but their stand-off is interrupted by a "dragon" (actually a dinosaur) that mauls their horses. They retreat to a crag the monster cannot scale, but are trapped without food or water. Conan recognizes some poisonous fruit growing nearby. The pair fashion a spear, coat the tip with poison from the fruit, and thrust it into the jaws of the monster. Although blinded, the raging monster pursues them by their scent. Overtaken, Conan whirls to face the beast and lures it to its death.
Conan and Valeria emerge from the forest and make their way to a strange walled city they spotted from the crag. There are no grazing herds or cultivated fields; they assume the city is deserted. When they arrive at the city, Conan forces open the door, long since rusted shut. The couple enter a bizarre twilight world. The city, which they come to know as Xuchotl, is a single massive structure completely enclosed and roofed over. A single great hallway runs the length of the city, but there are no other streets or open courtyards. It consists entirely of four tiers of rooms, chambers and passageways. Xuchotl is constructed of jade with traces of other exotic materials.
The pair separate to search the city's seemingly empty halls. Valeria encounters a man named Techotl whom she joins in a fray between two factions that dwell in the once populous city. Aided by Conan, they defeat their enemies. Techotl invites Conan and Valeria into the stronghold of his people, the Tecuhltli. They are welcomed by the rulers, Olmec and Tascela. As Conan and Valeria rest, Olmec recounts the history of his people.
The city of Xuchotil was built long before its current inhabitants arrived. In those earlier times, a slave — Tolkemec — betrayed his masters and guided the newly arrived invaders into the city where they put to death the original builders. The conquerors were led by two brothers, Tecuhltli and Xotalanc, who afterward ruled peacefully over the city until a feud developed when Tecuhltli stole the bride of his brother Xotalanc. The slave Tolkemec betrayed both sides for his own purposes and was exiled to the catacombs.
As Olmec tells his tale, Tascela becomes enraptured with Valeria. Later she has a slave attempt to drug Valeria with the black lotus, a powerful narcotic plant. Valeria manages to overpower the slave and attempts to force her to reveal the motive behind such treachery. However, the slave feigns submission and escapes.
Valeria's pursuit of the slave is interrupted when the Xotalancas breach the Tecuhltli defenses. In the end the Xotalancas are exterminated and only Conan, Valeria, Olmec, Tascela, and fifteen Tecuhltli defenders remain alive. When Conan and two warriors leave to scout the Xotalanc stronghold, Valeria is left behind while her wounds are tended.
Olmec attempts to force himself on Valeria, but he is thwarted by Tascela. She is revealed to be a sorceress and the stolen bride who originally started the feud. She plans to use Valeria's vitality to restore her youth. Erstwhile, Olmec secretly ordered his two warriors to slay Conan. Conan kills them and hurries back for Valeria. Returning to Tecuhltli, Conan finds Olmec bound and tortured. Conan releases him, but Olmec attempts another betrayal and Conan slays him.
Conan comes upon Tascela who has Valeria pinned to an altar. Conan, caught in a steel trap, watches powerlessly as Tascela proceeds with the sacrifice of Valeria. The scene is interrupted by Tolkemec who has returned from the catacombs, wielding a wand of terrible destructive power. Desperate for assistance against Tolkemec, Tascela frees Conan. Conan is able to defeat Tolkemec. Valeria, freed, avenges herself upon Tascela with a dagger thrust to the heart.
With the last inhabitants of Xuchotl slain, Conan and Valeria depart the dead city.