The History of Tékumel

60,000 years in our future, the vast Human star empire (with a technology level in the "indistinguishable from magic" range) discovered Tékumel, a planet circling Nu Ophiuchi. It would have been ignored, since it contained two hostile races, the subterranean Ssú and the aquatic Hlüss, possessing energy weapons and system-level space travel, but Tékumel was in a strategically important location. The humans defeated these races, placed them on reservations defended by force fields, destroyed vast tracts of poisonous native plant life and extensively terraformed the world, including cleansing the atmosphere, changing its orbit, and installing gravity generators at the core of the planet, all using energy drawn from other dimensions. A system of subterranean tunnels was built for supersonic transport vehicles. Tékumel became a hub of trade and a resort for the rich and powerful. Humankind's nonhuman allies came, as secretly did their enemies.
Hluss Hlüss Warrior

After a millennium as a pleasure planet for the wealthy, a great cataclysm occurred, ripping Tékumel's star system out of normal space and plunging it into the darkness of another dimension. Was this caused by some alien weapon, was it a side effect of the FTL drive, or was this the scheme of some immensely powerful interdimensional being? No one knows. From the global stresses of this event, earthquakes, volcanoes, tidal waves and other disasters befell Tékumel, and without supplies from the Human empire (especially iron for this metal-poor planet), civilization fell hard. The Ssú and the Hlüss rejoiced as the force fields keeping them in their enclaves failed.

Soon, there were no technicians to repair the great machines, though many still function to this day. How long this Time of Darkness lasted is unknown . . . perhaps 5,000 years. The first known return of civilization arose dozens of millennia before the game's current time period. The knowledge of the ancient technology has been lost, though mental techniques were developed for drawing on the power between the planes (which is what powered the machines of the ancients) and magic was born. Contact was established with extremely powerful, interdimensional beings that can only be called gods.

Most civilized areas are at medieval technological levels with some remote areas more primitive than that. Devices of the ancients, in that Clarke's Law range of sophistication, some still in working order, can be found, especially in the Underworld.

Tékumel is a hot planet. Temperatures in the inhabited temperate zone are similar to Earth's equatorial zone. Daytime temperatures in the summer can reach 125° F; nighttime temperatures in the winter go as low as 70° F.

The density of the planet is relatively low, making metals, especially iron, in short supply. Humans have adapted to this with the use of chlén hide, an animal hide chemically treated by the armorer's clan to form a lightweight substance with the hardness of bronze.

No riding beasts are known on Tékumel and the only draft animal is the ponderously slow chlén. Most merchant caravans use slave bearers, trained to carry large loads on their backs. Armies have no cavalry, relying on foot soldiers.

Five large empires cover the northern continent, on the scale of Imperial Rome or China. Intrigues, politics, and conflict is everywhere.