They are set within a series of artificially constructed universes, created and ruled by decadent beings who are genetically identical to humans, but regard themselves as superior, and are the inheritors of an advanced technology they no longer understand.
This technology enables the "Lords" (or "Thoans", as described by Farmer in his introduction to a role-playing video game)[1] to create novel lifeforms, and also to prevent aging or disease, making them effectively immortal.
Instantaneous travel within and between these universes is achieved by the use of "gates" which seem to function as teleportation devices, or as a means of creating wormholes between different regions of spacetime.
This planet consists of a series of cylindrical layers stacked one atop the other, to form an enormous, approximately conical tower (albeit much broader than it is tall).
For instance, the distance from the outer edge of the Amerind tier to the base of the monolith Abharhploonta is quoted as being 1500 miles (approximately 2400 km), while the surface area of the Amerind tier is quoted as being equal to that of North and South America combined (approximately 42 million square kilometers).
Paul Janus Finnegan was born in Indiana in 1918, and served in the American army during the Second World War, driving a tank.
In Dracheland, his identity is "Baron Horst von Horstman", whose coat of arms is a red jackass' head surmounting a fist with the middle finger extended.
She is driven out of her own universe by an ancient enemy that threatens to destroy all the Thoans, and takes refuge in the World of Tiers where she meets Kickaha.
Podarge, a terrible and extremely dangerous harpy, whose fantastic winged body was created by Wolff during his former life as Lord Jadawin, and who was given the brain of an ancient Greek woman by Wolff/Jadawin, appears periodically as both an ally and foe in the World of Tiers series.
Wolff enters the World of Tiers, arriving on the Okeanos level, and over the space of a few months regains his youth thanks to chemicals in the water and food.
In the second book, Wolff, now reinstalled as the Lord of the World of Tiers (but more humane and compassionate, after his amnesia erased the original Jadawin personality), enters a Universe constructed by his father, Urizen.
Urizen has kidnapped Chryseis, and Wolff finds himself reunited with his brothers, sisters and cousins, all of whom must travel from one dangerous planet to another to escape.
He meets three dispossessed Lords (one of whom is Anana) who are fleeing an army led by the Black Bellers – artificial intelligences capable of taking over the bodies of human hosts.
It is revealed that the civilization of the Thoans, including their understanding of the scientific principles behind their advanced technology, was destroyed during the war with the Black Bellers ten thousand years before.
It is strongly implied that this is all an exact copy of the Thoans' homeworld universe and that Thoa is itself artificial, but this question is not explored in the later novels.
They are all gated to the Lavalite world, a planet that changes shape periodically like the wax in a lava lamp, and which was created by Urthona.
The final book of the series takes place fifteen years later, Anana and Kickaha having been directed into a trap universe by Red Orc.
They escape, but Kickaha is forced by Red Orc to go in search of an entrance to a universe he found ten thousand years earlier but has been unable to return to.
The story culminates with Kickaha defeating Red Orc in hand-to-hand combat, and returning to the World of Tiers to resume his adventuring trickster lifestyle.
The structure of the world of tiers, with a central mountain or tower which the sun passes behind at night is equivalent to early Babylonian and Egyptian cosmological theories.
The placement of the Lord's palace at the highest level of the world is reminiscent of the home of the gods atop Mount Olympus.
The lord Jadawin uses intelligent ravens that roam across the world, observing, carrying messages, and reporting back to him, much like Odin in Norse mythology (See Hugin and Munin.
The moon of the world of tiers is modelled after Barsoom, from Edgar Rice Burroughs' novels, a homage which Farmer openly admits in the third book of the series.
By contrast, the character of Kickaha is a trickster, who avoids the affairs of the god-like Thoans wherever possible, and who survives and defeats his enemies by cunning, trickery and skill.