Ultima Segmentum is the biggest of the Imperium’s five great divisions of the galaxy, stretching east of Terra. It’s where you’ll find Ultramar, the Tau Empire, and the lawless frontier known as the Eastern Fringe, which makes it the setting for a huge chunk of Warhammer 40,000’s biggest stories.
What and where it is
The Imperium splits the galaxy into five segmentums, and Ultima is by far the largest. It lies to the east of Holy Terra, with its Segmentum Fortress at Kar Duniash.
Because it’s so vast, Ultima covers everything from prosperous core worlds to unexplored wilderness. Its eastern edge is the Eastern Fringe, the Imperium’s ragged frontier where its reach fades out.
The big players
Ultramar, the realm of the Ultramarines, sits inside Ultima Segmentum. So does the Tau Empire, which has been expanding along the Eastern Fringe for centuries.
It’s more than humans and Tau. The Sautekh Dynasty of Necrons holds territory here, and the region is littered with Ork empires, Craftworlds, and worse.
- Ultramar: home of the Ultramarines and one of the best defended regions in the Imperium.
- Tau Empire: a young, expanding xenos power on the Eastern Fringe.
- Sautekh Dynasty: one of the most powerful Necron dynasties.
- Ork empires of Charadon and Octarius: huge, brutal warzones.
- Craftworlds Ulthwe and Saim-Hann both have a presence in the region.
Worlds worth knowing
A lot of famous names sit inside Ultima Segmentum. Macragge, the Ultramarines’ homeworld, and Baal, the Blood Angels’ homeworld, are both here. So are Catachan, Valhalla, Attila, and Chogoris, which have produced some of the Astra Militarum’s toughest regiments.
The region also holds forge worlds like Ryza, Metalica, and Stygies VIII, plus T’au itself and the Tau sept worlds of Bork’an, Dal’yth, and Vior’la.
| World | Why it matters |
|---|---|
| Macragge | Ultramarines homeworld and capital of Ultramar |
| Baal | Blood Angels homeworld |
| Catachan | Death World, home of the Catachan Jungle Fighters |
| T’au | Tau homeworld |
| Ryza | Major Adeptus Mechanicus forge world |
| Prospero | Former Thousand Sons homeworld, now a ruin |
Regions, sectors and warpstorms
Beyond individual planets, Ultima contains whole named regions. The Galactic Core, the Red Scar, the Pariah Nexus, and the Kreen Scar are all here, along with the Maelstrom and the Storm of the Emperor’s Wrath.
The Great Rift cuts right through it. After the Thirteenth Black Crusade and Guilliman’s return, much of northern and northeastern Ultima was cut off inside Imperium Nihilus, stranded on the wrong side of the rift.
Why it matters
Ultima Segmentum is where the Imperium’s future is being decided. The Tau are still expanding, the Necrons are waking up, and the Great Rift has left huge swathes of it isolated.
If you’re reading about Guilliman’s Indomitus Crusade, the Plague Wars, or the wars against the Tau, you’re reading about Ultima Segmentum.
Key facts
- Ultima Segmentum is the largest of the Imperium’s five segmentums.
- It lies east of Terra, with its Segmentum Fortress at Kar Duniash.
- Ultramar, the Tau Empire, and the Eastern Fringe are all located here.
- The Great Rift splits it, leaving much of the north in Imperium Nihilus.
- Macragge, Baal, Catachan, and T’au are among its notable worlds.
FAQ
Where is Ultima Segmentum?
It’s the easternmost of the Imperium’s five segmentums, lying east of Terra. Its Segmentum Fortress is at Kar Duniash.
What’s the capital of Ultima Segmentum?
Kar Duniash serves as its Segmentum Fortress, the administrative and military hub for the whole region.
Which famous worlds are in Ultima Segmentum?
Macragge, Baal, Catachan, Valhalla, Chogoris, Ryza, and T’au are all here, among many others.
What is Imperium Nihilus?
It’s the half of the Imperium cut off from Terra by the Great Rift. A large part of northern and northeastern Ultima Segmentum falls inside it.