The Great Rift Explained: the Fall of Cadia, the Cicatrix Maledictum and the Indomitus Crusade

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The Great Rift is a giant tear in reality that split the galaxy of Warhammer 40,000 in two. It opened as Cadia fell to Abaddon's 13th Black Crusade, and it cut the Imperium into a half that can still see the Emperor's light and a half left in the dark. It is the reason the setting moved past the end of the 41st Millennium into a new age. Here is what happened, what the Great Rift is, and what it changed.

Lore page, last updated November 15, 2026. Summarised in our own words from codexes, campaign books and Black Library novels. The opening of the Rift is told from many points of view, and even its cause is still a mystery inside the setting. Where the lore differs, we say so.

The Great Rift in 30 seconds

Before the Rift: the Eye of Terror and Cadia

For ten thousand years, the most dangerous place in the galaxy was the Eye of Terror, the huge warp storm created when Slaanesh was born. It is where the traitor Legions fled after the Horus Heresy. You can read about that birth in our Chaos Gods page.

The only safe way out of the Eye was a calm stretch of space called the Cadian Gate, guarded by a fortress world called Cadia. Cadia's people trained for war from childhood, and for millennia they held the line. What almost nobody knew was that Cadia was also covered in ancient pylons, built by the Necrons, that helped keep the warp storms of the Eye in check.

The Fall of Cadia

Abaddon the Despoiler had thrown himself at Cadia again and again. In his 13th Black Crusade, he finally broke it. Part of his plan was a Blackstone Fortress, an ancient star fort he called the Will of Eternity. The Imperial Fists' giant fortress-ship, the Phalanx, managed to destroy it after Space Wolves boarders knocked out its shields. But Abaddon fixed engines to the broken pieces and steered them straight into Cadia.

Cadia's defenders, led by Lord Castellan Ursarkar Creed, fought to the end. They were joined by Saint Celestine, Inquisitor Greyfax and Belisarius Cawl, who even teamed up with the Necron Trazyn the Infinite to switch the pylons back on. It was not enough. The impact cracked the planet and the pylons failed. Celestine led the survivors off the dying world, and the famous words "Cadia stands" became a memory.

The galaxy tears open

A wave of warp storms raced out from the Eye of Terror and joined up with other storms until a scar of madness ran across the whole galaxy, all the way to the Hadex Anomaly on the far eastern edge. This is the Great Rift, or in High Gothic the Cicatrix Maledictum.

As it opened, a tide of warp energy and darkness swept out and dimmed the Astronomican. The Imperium calls this terrible time the Noctis Aeterna, "the eternal night", also remembered as the Blackness: for a while warp travel and astropathic messages became almost impossible, and many worlds were cut off and overrun. Daemons poured out across countless worlds, psykers screamed or burned as the Warp surged, and for a while it seemed the Imperium was finished.

What really caused it?

Most people will tell you the Fall of Cadia caused the Great Rift, and that is the simple version. But the official lore is careful to say nobody truly knows. Imperial scholars point to a whole pile of disasters that all happened at around the same time:

• The destruction of Cadia and its pylons.
• The sorcery of Magnus the Red during the Thousand Sons' attack on Fenris, home of the Space Wolves.
• Catastrophes in the webway, the Aeldari's hidden network of tunnels.
• The partial awakening of Ynnead, the Aeldari god of the dead, and the shattering of Craftworld Biel-Tan.
• Huge bloodshed and fire in the Damocles Gulf.
• The Chaos Gods reacting furiously to the return of Roboute Guilliman.

The honest answer is probably "all of the above, plus the Chaos Gods pushing very hard". Guilliman himself has his own theory: that Abaddon spent ten thousand years destroying worlds rich in Blackstone on purpose, and the fall of Cadia was simply the final trigger. The early books in the Gathering Storm series show the first cracks forming before the Rift fully tears open.

Imperium Sanctus and Imperium Nihilus

The Rift split the Imperium in two:

• Imperium Sanctus is the half on Terra's side. It can still see the light of the Astronomican, the Emperor's psychic beacon that ships use to navigate the Warp.
• Imperium Nihilus, the "dark Imperium", is the half on the other side of the Rift. Many of its worlds lost the Astronomican's light entirely. They are cut off and alone, and many have no idea if Terra still exists.

Crossing the Rift is extremely dangerous. The best-known safe road is the Nachmund Gauntlet, a narrow strip of calmer space near the Eye of Terror, watched over by the world of Vigilus. Because it matters so much, Vigilus has been attacked by Orks, Genestealer Cults, Drukhari and Chaos. A second route, the Attilan Gate, was later found by the Rogue Trader Katla Helvintr. Other, far more dangerous crossings are known too, such as the Straits of Epona, the Draedes Gap and the Straits of Andraste.

To keep the dark half from falling apart, Guilliman named Commander Dante of the Blood Angels as Lord Regent of Imperium Nihilus, giving the old hero the job of holding the line on the far side of the Rift.

Life near the Rift

The Rift does not just block ships. Time itself goes strange near it: some worlds have felt centuries pass in an instant, while others have been almost frozen. Whole star systems have vanished, stars have swollen red and reached out with arms of burning plasma, and ships have been attacked by monsters from nowhere. Inside the Rift, the Chaos Gods fight their own endless struggle, known as the War in the Rift.

Every race has its own name for it. The Orks call it Gork's Grin, the T'au call it the Mont'yhe'va, "the Devourer of Hope", and the Space Wolves of Fenris call it Everdusk. Other names include the Crimson Path, the Mouth of Ruin and the Warpscar. The T'au and the Aeldari suffered too: the storms killed millions of T'au and wiped out whole Aeldari colonies.

Guilliman and the Indomitus Crusade

Just as the Imperium seemed lost, Roboute Guilliman returned. With Belisarius Cawl's new Primaris Space Marines, he launched the Indomitus Crusade, a huge campaign to push back the darkness and reconnect lost worlds. The setting's new age is named after it: the Era Indomitus.

The crusade lasted around a century (some sources say about 112 years) before Guilliman broke it up. The reason was home. While he was away, Mortarion and the Death Guard had attacked his realm of Ultramar, which the Rift had cut off from normal warp travel. Guilliman crossed back to fight these Plague Wars, the story told in Guy Haley's Dark Imperium books.

The Rift today

The Great Rift is still open, and every story in modern Warhammer 40,000 takes place in its shadow. Tech-priests like Belisarius Cawl are studying the old pylon network in the hope of calming parts of it, and his latest novel is all about opening a new, stable path into the dark half of the galaxy. For now, though, the scar remains.

Where to read more

• Cadia Stands (Justin D Hill): Creed's last stand on Cadia during the 13th Black Crusade.
• The Gathering Storm: Fall of Cadia: the campaign book that tells the fall of Cadia and the first signs of the Rift.
• Dark Imperium (Guy Haley): Guilliman's return, the Indomitus Crusade and the Plague Wars.
• Avenging Son (Guy Haley): the first Dawn of Fire novel, set during the Indomitus Crusade.
• Belisarius Cawl: Archmagos (Guy Haley): Cawl's attempt to tame part of the Rift.
• Codex: Space Marines: the Primaris Marines who carry the Indomitus Crusade.

FAQ

What caused the Great Rift?

Nobody in the setting knows for sure. The Fall of Cadia during Abaddon's 13th Black Crusade is the most famous cause, but Magnus's sorcery at Fenris, disasters in the webway, the rise of Ynnead and other events around the same time are all blamed too.

What is the Cicatrix Maledictum?

The High Gothic name for the Great Rift. It means something like "the cursed scar".

What is Imperium Nihilus?

The half of the Imperium on the far side of the Rift, cut off from Terra and often from the Astronomican. Commander Dante rules it as Lord Regent.

How do ships cross the Great Rift?

Very carefully. The Nachmund Gauntlet, guarded by Vigilus, is the best-known stable route, and other safe paths are rare.

Is the Great Rift closed now?

No. It is still open, and it shapes everything in the current era of Warhammer 40,000.

More lore: Abaddon the Despoiler, Roboute Guilliman, Commander Dante, the Chaos Gods and the Emperor of Mankind.

Lore summarised in our own words from Black Library novels, codexes and community wikis. Warhammer and all related names are trademarks of Games Workshop; WIZY is an independent fan site.