Nimbosa

Nimbosa is an Imperial industrial hub on the T'au border, valuable enough that Brightsword's cadres seized it in the Second Sphere and butchered Vostroyan defenders at Koloth Gorge. The later Nimbosa Crusade brought Black Templars and Imperial Fists through the orbitals and down onto the surface. The Imperium holds it again, but the scar stays in both empires' histories.