Lost Tribes of the Underworld

This idea literally came to me in a dream, which almost never happens and is to be savoured when it does.

• Woadsmen

Were boarhunters, raiders, builders of longships and stone circles. Upon the advent of a more technologically advanced race they were lured below by the false promises of worm-like gods.

Cloaked in symbiotic mold. Not luminous. Why would you give away the advantage of surprise? Deadly poisonous, including to woadsmen, who begin acclimatization at birth but still suffer from blinding headaches and auditory hallucinations. Combat, fast movement shakes off the spores. They will stalk you in the dark for leagues, gently infecting your brain, making you doubt your own sanity, so that when they finally attack it comes as a relief. Less powerful if you know what they are beforehand.

Have few children and love them fiercely. Perfectly accurate thousand-year record keeping lets them keep track of the stars and cast astrological magics, even underground.

• Wakaddish

Were whalers, traders, weavers and woodcarvers. Driven below by a storm that never ended. They believe in a culture hero who angered a thunderbird, but none of them even really remember what wind is.

You don't know this, because you don't know most things, but there are whales below. Why wouldn't there be? There are gaps in the continental shelf, holes in the floor of the sea, and whales are inquisitive. The whales below are eyeless, white, wrinkled, able to squirm through holes, often smaller but sometimes much larger. Some have learnt to breath sulphur, others make do with the still and tasteless air.

The Wakaddish hunt the whales below. They've had to make adaptations - their canoes are now pumice, their spears mostly bone. Wood is beyond price down there. They set up camp around black lakes or bubbling fumaroles and wait for days, weeks, years. For the leviathan to emerge, and take its last breath.

• Nephtain

Were temple builders, devil-worshippers, eaters of unleavened bread. Escaped when their brethren were taken as slaves, wandered the desert for far too long, fled below out of sun-madness and desperation. Still fear thirst above all.

Each subtribe of Nephtain has its devil, which is toted before them in its devilbox. If they find a home they will lay it to rest and build a city around it. One subtribe has achieved this - Maggothum is nicer than its name would suggest, as long as you placate the maggots, who prefer their cut in pus but will take it in most other currencies. All the others are still wandering.

Have complicated dietary customs which seem absurd at first but, if followed closely, are of immense nutritional value.

• Carmatians

Were horse archers, goldsmiths, drinkers of fermented mare's milk. No-one knows why they came below. Perhaps the promise of gold, or new civilizations to despoil. Or perhaps the world grew colder and they feared the lengthening of the winter. A proud people, the Carmatians prefer the former story.

The Carmatians brought their horses. The Carmatians are nothing without their horses. But what began as a happy marriage between man and beast soon grew bitter and acrimonious. Horses eat too much, can't climb, have to be killed if their legs break. The Carmatians still ride their stunted steeds through limestone valleys and down slopes of scree but they despise them for the weaklings they are. They are the laughingstock of the underworld and they know it. They are clinging to an outdated strategy. Even their pointy hats are stupid.

The Carmatians, themselves, are not stupid. They are looking for a way out. The khagan has promised a fortune in gold to anyone who can breed her a mount worthy of her people. She doesn't care if it's a lynx or a centipede or some kind of suction-hooved pony that can go up mountainsides like the one in The Man From Snowy River. She doesn't care if it's two human beings surgically joined together. All she wants is swiftness, endurance, agility, terror. And when she gets it she will shatter the globe from the inside out.

• Unpi

Were workers of clay, farmers of maize, dollmakers and eschatologists. Led below by Locust Sister after a great flood. Not too worried about it. It's happened before and will happen again.

The Unpi know from their grand calendar that time is circular. Everything that happens has happened before, and every so often everything must be reset so it can all happen again. But it can't be allowed to happen again in the exact same way - how boring would that be? So Locust Sister intervenes at the end of each age to lead the Unpi people into a new world while the old one is wiped away. This has happened five times so far. Right now we're about two-thirds of the way though the cycle.

The Unpi see any attempt to return to the surface as perverse, like time travel, or necromancy. It's gone. Don't dwell on it. Their prophecies are spookily accurate, though the words are wrong, since they aren't actually prophecies - just stories handed down from the last age, when everything was the same but also different. They're a peaceful people who execute criminals by imprisoning them in smokehouses until they suffocate. They know you're going to commit a crime before you do and will happily execute you before you've committed it. They're fatalistic to a fault and will do (and suffer) horrible things just because that's how it happened last time. They know they'll all be reborn.

The Unpi fear only one thing: the trickster spirit Katapaxchu, or Cornhair. He alone has the power to make things go other than they are supposed to. If left to his devices he will upset the entire course of the universe. Even tiny changes have the potential to disrupt all reality and return everything to the formless chaos of the Time Before. Do not allow yourself to be interpreted as an agent of Katapaxchu.

• Kuk Yam

Were pearl divers, poets, hunters of crocodiles, deeply concerned with politics. Chased below by a plague which pocked the skin and shrivelled the mind, brought to them by trading-partners from across the sea. Bought their passage with the souls of their ancestors.

Always know what direction north is. Their language doesn't even have words for left and right - they don't need them. This was fine on the surface but it is insanely useful underground, where there's often literally no other way of telling. It's cultural, not some mutation - they are taught when they are kids and always remember it.

The Kuk Yam have an empire. They have maps of their empire, and the maps are actually useful. They are the only people who can reliably make their way across thousands of miles of cavern without having to memorize every single twist and turn. Hundreds of races swear obeisance to them. They would be satisfied, if only they could reclaim the souls of their ancestors. But even their hardiest explorers cannot find the creature they sold them to. Flawlessly guided expeditions descend into the bowels of the earth on a weekly basis and most of them return, but empty-handed. The Greathouse of the Cartographers grows longer every day, and the frontiers of the empire advance correspondingly, but the captured ghosts of a hundred generations are still out there somewhere, buried. Cursing their children's names.

The Kuk Yam are sickened by guilt. They would forfeit everything they had in a heartbeat if it would allow them to revoke their betrayal.