So 40k the Imperium's main saying is 'Kill the Mutant, Burn the Heretic, Purge the Xenos/Unclean (depends on who you ask)' Grim dark gothic western space fantasy. Really interesting and very complicated, we will all be humans, with the possibility with some flexibility in the future. 

This is based on Only War which follows regular humans, the baseline non-enhanced humans of the Imperial Guard. These guys are the basic military arm of the Imperium of Man. But, on a galactic scale, the Astartes are the baseline, which one Astartes (genetically modified super soldiers of the Imperium) is worth a hundred Guardsmen. But don't forget they are baseline, so the other races, like say the orcs, also lesser compared to the Astartes, but they hold a better chance compared to a single guardsman. Or you could have an elder, which could probably kill an Astartes, or another chaos space marine that could also go toe to toe with one. Scaling up to titans which could decimate entire chapters of Astartes with a single blast. 

But, at the moment, we are starting off with more of a horror aspect. A small group of people cut off from help, with what they have with them, and what they have in the bar. Set out to help those below and to begin the process of trying to help.