Video games have always treated guns with a certain reverence, from the wicked grin of Doom's marine when he picks up the shotgun, to the pornographic customisation options of modern Call of Duty. Warhammer: 40k Boltgun takes this to its absurd logical endpoint. In the opening level, your hulking space marine discovers the titular firearm on a literal altar, a chorus of angelic voices chanting as you pluck the weapon from its pedestal. "A Holy Relic!" burbles your accompanying servo-skull as you lock and load. "The Emperor Provides!"
It's a fitting introduction to Boltgun's eponymous weapon, not just because the game revels in the excess of both 40k and mid-nineties shooters, but also in how it reflects upon its strengths and, by association, weaknesses. No other weapon is afforded such treatment, which is appropriate because no other weapon is as good. Boltgun's boltgun is the virtual firearm perfected, so innately satisfying that it blows away the game's own power curve alongside the hordes of daemons you'll slaughter with it.
Unlike how it introduces its signature firearm, Boltgun doesn't stand on ceremony getting you into the action. A brief cutscene summarises the situation. The Adeptus Mechanicus has picked up strange readings in the forge world system of Graia, and dispatches you, along with a small team of other Space Marines to investigate. But your team is killed in the initial drop, leaving you alone to battle a rapidly developing incursion by the forces of Chaos.