Thoas

Thoas is a tidally locked world in the Ultima Segmentum where the Ultramarines destroyed an Ork empire during the Great Crusade. Its pre-Imperial human civilisation poisoned itself, and an Ork empire later established its seat of power among the irradiated ruins. This entry concerns the Thoas associated with the campaign of Roboute Guilliman, Lord of Ultramar.

The XIII Legion, the Ultramarines, purged the neighbouring systems and concluded the war on Thoas itself. The planet has two moons, and its crust remained uninhabitable to unaugmented humans after the fighting. Guilliman’s compliance, the Imperial term for bringing a world under its authority, left the planet a lifeless relic rather than a new tithe world, that is, one that supplies the Imperium with regular levies of resources or population.

Thoas remains significant as an early Ultramarines example of an empire that consumed itself. This entry retains its Ultima parent and does not classify it as a hive world or as a homonymous location in another Segmentum.