The Skaven: The Great Under-Empire

Somewhere beneath every city in the Mortal Realms, something is listening. Press an ear to the deep stone and you might hear it: the scratch of a million claws, the hiss of chemical fires, the squealing of a civilization that has never once been counted because it breeds faster than anyone can tally. The skaven are the great secret rot at the root of the world, a boundless empire of scheming rat-men who believe, with total sincerity, that they are destined to devour everything. The terrifying part is that they might be right.

The Under-Empire

The skaven do not hold a realm of their own the way other peoples do. Instead they hold the space beneath all of them at once. Their tunnels honeycomb the foundations of the Mortal Realms, threading through rock and root and the buried bones of dead ages, so that the skaven are simultaneously everywhere and impossible to pin down. This subterranean sprawl is the Under-Empire, and it obeys no borders, respects no realm's laws, and can vomit its teeming legions up into the light almost anywhere a floor is thin enough to gnaw through.

Their numbers defy belief. Skaven breed in colossal, seething multitudes, and they spend those multitudes with a callousness no other faction can match. A warlord who loses ten thousand ratkin before breakfast simply sends for twenty thousand more. This is an army that treats its own soldiers as ammunition, and it is one of the reasons the skaven are so hard to defeat: you cannot bleed dry a foe that regards its own blood as limitless.

The Great Horned Rat

Every skaven bows, at least in theory, to the Great Horned Rat, their monstrous deity of decay, treachery, and swarming ruin. Once a lesser power, the Horned Rat has clawed his way up to take a seat among the true gods of Chaos, and his ascension has made his children more dangerous than ever. He embodies the skaven perfectly: patron of plague and paranoia, of the knife in the dark and the empire built on lies, his blessing rewards not honour but cunning survival. To learn how he fits among the other dark powers, see the Ruinous Powers in the Mortal Realms.

The Great Clans

Skaven society, if the word even applies, is carved up among specialised clans, each a sprawling institution built around a single obsession. The warlord clans field the endless infantry hordes that form the bulk of any skaven army. The warlock-engineers are mad scientists who harness raw magic into sputtering, catastrophic war-machines. The masters of beasts stitch and breed monsters in reeking flesh-pits, birthing rat-ogres and worse. The plague-priests cultivate pestilence as a form of worship, and find a natural, uneasy kinship with the followers of the Maggotkin of Nurgle. The assassins sell murder and shadow to the highest bidder. And above them all scheme the grey seers and verminlords, sorcerer-prophets who claim to speak for the Horned Rat while pursuing agendas entirely their own.

These clans do not so much cooperate as compete, and the ruling council that supposedly governs them all is a nest of vipers where every seat is won and kept by betrayal. It is a small miracle of malice that the skaven accomplish anything at scale, and yet they do, again and again, because their shared appetite for conquest briefly outweighs their appetite for stabbing one another in the back.

Warpstone and Mad Invention

The engine of skaven power is warpstone, a solidified form of raw Chaos magic that the ratkin mine, refine, eat, and weaponise with reckless abandon. In their hands it becomes fuel for lightning cannons, choking green gas, teleportation devices, and doomsday contraptions that are as likely to annihilate their own crews as the enemy. Skaven invention is brilliant and insane in equal measure, a firework display of genius perpetually one spark away from catastrophe. Their engineers dream of weapons that could crack a realm, and they are reckless enough to build them.

This makes them a peculiar horror to their enemies. The proud sky-fleets of the Kharadron Overlords, the volcano-forged lodges of the Fyreslayers, and the artillery of the free cities can meet most foes on known terms, but there is no predicting what a skaven war-machine will do, least of all to its owners. To fight the ratkin is to fight a technology with no safety catch.

A Civilization Built on Betrayal

Treachery is not a flaw in skaven culture; it is the culture. Every skaven expects to be betrayed and plans accordingly, which produces a society running on constant, exhausting paranoia. Cowardice is rational, loyalty is naive, and the surest route to advancement is to let a rival take the risk and then claim the prize over their corpse. Bizarrely, this makes them formidable rather than fragile, because a skaven horde that is winning becomes an unstoppable avalanche, every ratkin suddenly brave now that the danger belongs to someone else.

It also makes them the perfect opportunists of the Mortal Realms. Skaven rarely start a war they cannot exploit; instead they wait for others to weaken one another and then swarm up from below to feast on the wreckage. When the Stormcast Eternals and the armies of Chaos grind each other down, it is often the skaven who profit, and the defenders of the Cities of Sigmar have learned to fear a quiet cellar as much as an open siege.

Everywhere, All at Once

What makes the skaven such an enduring threat is that they can never truly be conquered, only driven back into the dark from which they always return. Their gnawing tunnels can breach any realm; their numbers can never be finally counted; and their god grows stronger with every plague and every lie. They are the setting's ultimate reminder that no fortress is ever entirely safe, because the enemy is not merely at the gates but under the floor. For the wider picture of the powers they scheme among, see the Grand Alliances of the Mortal Realms, and never, ever trust a silence in the deep places of the world.