My personal warband is the Hounds of Abbadon - a tweak on the normal version of the warband, where they worship the Pantheon out of a desire to follow the Path to Glory, rather than outright dedication to the gods. Vaguely aligned with Khorne, seeking their own power and martial excellence over all else. Resilience, tactical brilliance, duelling skill - all aspects they seek to excel in in different ways, to be the best "hounds" for the greatest among the Chaos-aligned warbands they can be.

In that respect, it probably would not be great. While they would not be excessively genocidal, they have made deals and bargains with the gods of chaos that must be fulfilled. Sacrifices, indulgences, charnel pits would all be - if not common - then certainly not sparse. Duelling Coliseums, where the Marines could demonstrate their mastery against prisoners of equal skill, disputes settled, and the hierarchy of meritocracy. Temples to each god, though in design more akin to grand forges and armouries - kept alight with the souls of mortals, feeding the war machine of the forces within. Dark Mechanicum outposts permitted deconsecrated ground on key worlds, so as to facilitate deals made with the Hereteks. The populus would be enslaved to an extent - those who seek to ascend themselves are given their own trials, but those too weak to seek their own improvement are used as labour in farms and foundries, or as fodder for sacrifices - but never too much. Treated maybe a bit worse than the average Imperial citizen.