Savlar is a blighted mining world condemned to serve as a prison, its scarred surface honeycombed with mines worked by generations of convicts and their descendants. The air is foul, the water tainted, and the labour murderous, so that the wretched populace survive only by huffing the very chemical stimulants they are set to extract, breeding a society of desperate, drug-addled outcasts.
From this misery the Imperium wrings profit and soldiers alike. The world furnishes the notorious Savlar Chem-Dogs, penal regiments of the Astra Militarum drawn from its criminal masses, their loyalty enforced by the lash and the threat of worse. Ill-disciplined, self-serving and reeking of the narcotics they cannot live without, the Chem-Dogs are nonetheless flung into the Imperium's most hopeless battles, where their expendable lives buy time for better troops.
Such regiments are watched with contempt and suspicion by the commanders who deploy them, for the Savlar fight as much for plunder and their next fix as for the God-Emperor. Yet in the grinding attrition of galactic war, even the dregs of Savlar have their uses, and the world grinds on, exporting its ore and its criminals to feed an Imperium that regards both as equally disposable.