Marathag Craftworld

Marathag is a very new Craftworld, led by Ariel Ysggad and crew/inhabited by Eldar outcasts and exiles, trying to turn it into a 'proper' Craftworld while fighting off Chaos, Orks, their dark cousins, and Adeptus Mechanicus forces intent on taking and studying the Craftworld.

History
Almost nothing is known about Marathag's history before its recent discovery, but Navarre and Ariel Ysggad have theorized that at the moment of the Fall of the Eldar, the Craftworld was not yet complete, perhaps the result of a last-ditch effort of Eldar to escape; when the Fall came, Slaanesh was born, and the Eye of Terror was created; they believe that the Craftworld may have become pulled into the warp in a manner similar ot Imperial vessels(as opposed to the Eldar Webway) and drifted in the Warp for thousands of years

All that is known for certain is that Marathag Craftworld was discovered in Chaos forces loyal to Slaanesh in 997.M41 floating in the void above the Krimzon system, having apparently come out from the Devil's Eye, a massive Warp rift nearby.

Before the Slaaneshi could take possession of it, a large fleet of Dark Eldar appeared and attacked them; Ariel Ysggad first came to Vigo to investigate increased Druchii activity in the region; he believes that the Dark Eldar somehow knew about its impending reappearance.

As the Slaaneshi and Druuchii fought, a large allied Imperial/Eldar fleet, led by Karlees Navarre and Ariel Ysggad arrived, took the two enemies by surprise, and routed them.

While the Eldar pursued the Dark Eldar, the Imperial forces secured the system and discovered what the Dark Eldar and Slaaneshi had been fighting over; Navarre and a small force of Stormtroopers teleported aboard, and discovered that not only was the Craftworld uninhabited, it had never been inhabited; it was then that Navarre started to formulate his theories regarding the Craftworld's origins.

To avoid war with the Eldar, Navarre invited them to take possession of it(much to the indignation of the Adeptus Mechanicaus when they learned about it) on the condition that the Craftworld would remain in the Vigo Sector for a thousand years, and remained allied with the Imperium for all that time; many Eldar commanders refused to accept and almost started the war anyway, but Ariel Ysggad preempted them, taking control of the Craftworld, naming it Marathag(Face of Death) for its empty, uninhabited state, crewing/populating it with his followers, and invited other exiles to join him.

Since then, Ariel and his people have slowly opened up much of the Craftworld to habitation, and slowly increased both their numbers and resources; and fought off many attempts to capture or destroy the Craftworld made by the Dark Eldar, Orks, Chaos, and the Adeptus Mechanicus.