Editing Imperial Worlds (section)

===Dead Worlds===
Exterminatus isn't the only way planets die. Ecological disaster, sudden celestial events, alien invasion, someone disengaged from the warp too close to the planet and accidentally the atmosphere... (assuming you can Warp into a star system or near a planet, the lore happily contradicts itself on this constantly because fuck consistency). Unlike Quarantine/Forbidden Worlds (see below), these aren't strictly forbidden for colonization, just that the work required to make them habitable is prohibitively expensive for the negligible gain in resources. Most would require either completely isolated arcologies, underground cities, or huge terraforming projects. Tyranids create these worlds en masse: after they nom all the life on the planet, they will then turn to draining the planet of its core, atmosphere, and any water still remaining before setting off for new real estate.