The Diasporex was a nomadic civilisation of humans and aliens that were wiped out by the fledgling but xenophobic Imperium of Man.
The Diasporex evolved as a group of human refugees fleeing their worlds, in a response to the many horrors that many human-worlds suffered since the Age of Strife. Eventually these humans made allies with other spacefaring alien races creating a powerful nomadic nation. During the last days of the Great Crusade in the early 31st Millennium, the Iron Hands Legion encountered the fleets of the Diasporex. When the humans refused to accept Imperial Compliance and abandon their alien allies, the Space Marines of the Iron Hands and Emperor's Children waged a war to forcibly bring the humans under the banner of the Imperium.
The aliens were mercilessly executed and the human crew members were forced into labor camps under the so-called benevolent rule of the Emperor.
The Diasporex lived aboard a vast collection of starships, which were maintained by a network of hydrogen collector space stations around various stars.