It is set in the fictional Hyborian Age and concerns Conan entering a lost city whose degenerate inhabitants are entangled in a murderous blood feud.

Due to its dark themes of decay and death, the story is considered a classic of Conan lore while also cited by Howard scholars as one of his best tales.

[1] In the jungles far to the south of any known civilized or barbarian kingdoms, Valeria of the Red Brotherhood flees persecution after murdering a would-be rapist.

Conan's stand-off with Valeria is interrupted by a dragon (actually a dinosaur, described with the characteristics of a Stegosaurus and Allosaurus) which mauls their horses.

Acting quickly, he coats the tip of a spear in poison and pierces the dragon's lower jaw with a well-aimed throw.

Soon, Techotl invites Conan and Valeria into the stronghold of his tribe, the Tecuhltli, where are welcomed by the king and queen, Olmec and Tascela.

Nails driven into a pillar inside of Olmec's stronghold keeps count the number of slain rivals, and provides the title for this story.

Eventually, all of Xotalanc's troops are exterminated while Conan, Valeria, Olmec, Tascela, and fifteen Tecuhltli warriors remain alive.

Howard's Puritan adventurer Solomon Kane explored the lost African city of Negari in "The Moon of Skulls", published in Weird Tales in 1930.

In "Xuthal of the Dusk" (published in the September 1933 issue of Weird Tales as "The Slithering Shadow"), Conan and a female companion discover an inhabited lost city and encounter its resident femme fatale.

In early 1935, he remarked to Novalyne Price: "You see, girl, when a civilization begins to decay and die, the only thing men or women think about is the gratification of their body's desires.

When you have a dying civilization, the normal, accepted life style ain't strong enough to satisfy the damned insatiable appetites of the courtesans and, finally, of all the people.

'"[4]The idea that would become "Red Nails" continued to germinate in Howard's mind, and later that year he began the actual writing of the tale.

Howard explained the circumstances surrounding his need and made it clear that he understood that Weird Tales was undergoing its own share of financial difficulties due to the Depression.

However, he felt moved to state in no uncertain terms, "A monthly check from Weird Tales may well mean for me the difference between a life that is at least endurable and God alone knows what.

In a letter to H. P. Lovecraft he confided, "As for my own fantasy writing, whether or not I do any future work in that field depends a good deal on the editors themselves.

At the time, he shared his thoughts with Clark Ashton Smith, another colleague: "Sent a three-part serial to Wright yesterday: 'Red Nails,' which I devoutly hope he'll like.

E. F. Bleiler placed "Red Nails" "among the better Conan stories," citing its "Extravagant adventure embodying a considerable amount of antiquarian lore and imagination.

The story was later adapted by Roy Thomas and Barry Windsor-Smith for issues #2-3 of the Marvel Comics magazine series Savage Tales.