From Lexicanum

Segmentum Obscurus is to the north of Holy Terra and is home to many of the Imperium's problems. The Segmentum Naval Base is located at Cypra Mundi and it is home to many other notable planets.

Like the Segmentum Pacificus, it has had no contact with the Tyranids in the history of the Imperium, but a creature on the planet Fenris, the Kraken, has been hypothesised to be part of a failed Tyranid invasion force many millennia ago.

The main feature of the segmentum is the Eye of Terror. Around it is centred many significant Imperial planets, including:

• Cadia
• Fenris
• Mordian
• Caliban - destroyed
• Medusa
• Scintilla (Calixis Sector)

The Cadian Gate is guarded by various forces around its vicinity, but is often the site of the various Black Crusades.

It is also home to various human and alien planets and territories, including:

• Ulthwé Craftworld
• Ornsworld - One of the Ratling homeworlds
• Several Ork worlds
• The Ghoul Stars - Home of the evil Cythor Fiends

Other Segmentums

• Segmentum Pacificus - South West
• Segmentum Solar - South
• Segmentum Tempestus - Far South
• Ultima Segmentum - South East