"It was a black reality, an empire of black magicians, steeped in evil now long forgotten. It was finally overthrown by the Hyborian tribes of the west. The wizards of Acheron practiced foul necromancy, thaumaturgy of the most evil kind, grisly magic taught them by devils." -- Robert E. Howard: "Hour of the Dragon"
An ancient kingdom, extinct in Conan's time, founded by a northern offshoot of the Lemurian survivors several thousand years after the Cataclysm.
Its area roughly corresponded to Aquilonia, Argos, and Nemedia, and its dominion later extended over western Koth, Ophir, and Corinthia. The latter three nations were also under the hegemony of Old Stygia at one time, apparently falling to Acheron at a later date. It seems likely that Acheron overextended itself by annexing these Stygian satellites, leaving its northern frontier vulnerable to the subsequent Hyborian invasions.
The exact chronology of Acheron is shaky; but it seems to have flourished for about 2,500 years, a theocracy under the control of wizards. The barbarian pressure of the more vigorous Hybori pouring down from the north ultimately destroyed Acheron. Its demise took place 3,000 years before the time of Conan.
The resurrected wizard Xaltotun attempted to restore the ancient kingdom, but was frustrated by Conan.
- Budra: A kingdom in existence at the time of Acheron's fall, nothing is known of it save its name. (Conan the Rogue)
- Cetriss, Palace of: An ancient, abandoned palace carved into a cliff of living rock in a canyon amid the crags of the Dragon's Spine in eastern Stygia. It was the abode of Cetriss the mage during the days of Old Stygia, 3000 years ago. It was here that he created a living flower-fungus hybrid, the green lotus. He used the sorcerous powers of the lotus to keep the world-hungering Empire of Acheron at bay. (Conan and the Emerald Lotus)
- City of Brass: A ruined, ancient city that lies in the desert of eastern Shem. The city is the ruins of the Holy City of Nithia, destroyed by the Acheronian army three thousand years before Conan's age. Marvelous verses are writ in gold on its marble walls. It is rumored to appear only once every century, and to be the resting-place of an incredible artifact, a statue called the "Grim, Grey God". (Conan and the Grim Grey God, Conan and the Amazon)
- Croton: A wicked town on the borderlands between Aquilonia and Nemedia. It is claimed by both and garrisoned by neither. It is a resting-place for outlaws and criminals of all kinds. The great Acheronian city of Karutonia once stood here. The ruins appear as hills surrounding the town. (Conan the Bold)
- Edom: An ancient, dead empire, whose cities were destroyed by a blast of fire directed by the god Votantha. Thought to have existed since the fall of Acheron, Edom died when its last city, Yb, was destroyed seven hundred years ago for its sins against the proud city of Sark. (Conan the Outcast)
- Gray Despair, Sea of: A bleak wasteland of salt, located in west-central Corinthia. The center of the wasteland was rumored to be the site of an ancient city that was razed during the Age of Acheron. All the land surrounding it as far as the eye can see was salted so that nothing would ever grow there. (Savage Sword #221, "Werewoman", by Roy Thomas)
- Horns of Shushtu: A remarkable mountain complex in the Black Lands, the tops terminate in two nearly identical crags, one colored black and the other one white. To the west of the "Horns" lies a great inhospitable desert. Waterholes are few and far between, although one permanent oasis lies a day and a half march from the mountains. A pass runs between the twin crags and the ruins of an ancient road lies there. Vertical stone walls lie along the road and these are covered with pre-Pythonic hieroglyphs and pre-human carvings. To the east of the peaks is a large temperate plateau, where the cyclopean ruins of a city of Acheron lie. The center of the plateau is a depressed valley, with all the mountain streams running into and forming a broad, dark lake. The ruins of a city built by prehistoric snakemen lie to the west of the lake. A colony of Acheronian refugees built New Python atop these ruins. There are also the ruins of a stronghold on the eastside of the lake. Beneath this stronghold lies the treasure of Python, the ancient Acheronian capital. (Conan and the Treasure of Python)
- Ishdaris: An ancient power, presumed to be contemporaneous with Acheron. It's black armies' worshiped Ikribu as a god of war. (Ring of Ikribu)
- Kara-Shehr: So-called City of the Dead, a ruined outpost of ancient Acheron, situated southeast of the Vilayet Sea. (Conan the Barbarian #35, "Hell-Spawn of Kara-Shehr", by Roy Thomas)
- Karutonia: A great city of Acheron, it stood upon the foothills of the Border Range on the Aquilonian side. At one time over a million people lived there. (Conan the Bold)
- Kheba: An ancient power, presumed to be contemporaneous with Acheron. It's black armies' worshiped Ikribu as a god of war. (Ring of Ikribu)
- Khet: The fabled "City of Scorpions", its ruins lie in Stygia along the River Styx. A contemporary of Acheron, the city was dedicated to the worship of the minor, Acheronian goddess, Selkhet. During the "Years of Dissolution", the city was abandoned and eventually fell into decay and ruin. (Conan the Rogue)
- Kuthchemes: A ruined city with an ivory dome, situated in the desert southeast of Shem, to the southwest was the Big Bend of the Styx. The city flourished 3000 years before Conan's time, contemporaneous with Acheron and Old Stygia. The ancient god Zug lives at the bottom of a pit beneath the ruins, next to the subterranean "River of Darkness". (Black Colossus, Flame Knife, Conan the Barbarian #250, "Chaos Beneath Kuthchemes", by Roy Thomas)
- Lemurians: The race of Lemuria. After the destruction of their land, the Lemurians fled to the eastern shore of the world-continent where the ancestors of the Khitans enslaved them for many centuries. Later they were able to revolt successfully against their masters and migrate westward. This migration may have been prompted by racial memories of the ancient colony of Lemuria-of-the-West. There were in ancient times two main lobes of Lemurian movement: the southern, which eventually founded Old Stygia, and the northern, which founded Acheron. A much later movement of Lemurian peoples out of the deserts and steppes of the Far East gave rise to the Hyrkanians. (Hyborian Age I, Mirrors of Tuzun Thune)
- New Python: A ruined city located on the plateau east of the "Horns of Shushtu". The city was built by Acheronian refugees on the ruins of a prehistoric snakeman city. It was to this place, that all the magical artifacts and treasure of the original Python were brought after its destruction by the Hyborean tribes. (Conan and the Treasure of Python)
- Nithia, Holy City of: Also known as the "Brass City of Nithia", it is an ancient city of Ibis worshippers. The city was contemporaneous of the Acheronian Empire. White marble walls and huge brass gates protected Nithia, nine days travel from the nearest city. The "Seven Fountains of Ibis" kept the city green and flourishing at the center of the Nithian Desert. The priest-kings of Nithia were descended from Atlantean kings. In the crystal-domed temple of Ibis was kept the statue of an incredibly ancient Atlantean god, called the "Grim, Grey God". The statue was carved from a pearl twice the size of a man's head. When the Acheronian warlord Dhurkhan Blackblade razed the city and claimed the statue, the priest-kings magic buried it in the ruins of the city, in a sandstorm lasting twenty-three days. For the next three-thousand years the city lie nearly forgotten, remembered only as the fabled "City of Brass", in what became the deserts of eastern Shem. (Conan and the Grim Grey God)
- Pyrrophlagalon: Also known as the "City of the Burning Souls", this lost capital was the very black heart of Acheron. The city was the seat of the House of "Ixion the Devourer" and his two sons, the dread sorcerer Xaltotun, and Dhurkhan Blackblade, the Supreme Warlord of Acheron. The city's location is not known. (Conan and the Grim Grey God)
- Python: So-called City of Purple Towers, ancient capital of the evil empire of Acheron, its extent was ten times that of Luxor, Old Stygia's greatest city.
- Tartarus: The seat of the Acheronian Empire. The army that razed Nithia came from here. The city's location is not known. (Conan and the Grim Grey God)
- Xaltana, Tomb of: Located high in the northern Border Range of Nemedia is the long-lost tomb of Xaltana, the Witch-Queen of Acheron. Concealed in the mountains by the magic of illusion, the tomb was buried beneath the temple of an ancient demon-god. (Marvel Graphic Novel, "The Witch Queen of Acheron", by Don Kraar)
References: Hyborian Age I, Hawks over Shem, Black Colossus, Conan the Buccaneer, Hour of the Dragon, Conan and the Treasure of Python, Conan and the Grim Grey God, Conan the Bold, Conan the Rogue, Conan and the Emerald Lotus.