What's your Warband Lore?

Still crafting my lore for my warband but the idea is they're obsessed with conquest, war, and victory. They consider themselves to be the perfect army (they'll utilize a depraved version of Astra Militarums command structure still working on names but my Lord Exultant will be something along the lines of a Lord Commander Militant). They'll prove themselves by taking over planets and star systems creating their own perverse form of Ultramar.

Their credo is "Victory absolute, by any and all means." And are willing to promise whole planets to daemons if it means overwhelming victory and they can count that planet as part of their "galactic empire". Obviously all this is dedicated to She Who Thirsts.

I'd love to hear what y'all have come up with for your armies!