I dunno. Can you really communicate the depth of what the Emperor is about, the scope He takes on in the minds of the Imperium's people, with just the intro blurb? I think you have to build on that with establishing shots and explain it through the story rather than like 30 minutes of unrelated characters doing a flashback to set it up.
For many 40k film concepts, you don't need to do a whole lot. It's easy to establish that the God-Emperor is the sole deity of the Imperium and humanity, that he once walked amongst men, and that he ascended the Golden Throne on Terra to guide us. It's missing a lot of the Emperor's real story, but that's arguably a good thing. If the film is from the perspective of the Imperium's people, then that's all the context you need at first. It provides an introduction that lets you add in more and more of the real story, going from loyal Imperials to the Chaos side of the story to eventually a Horus Heresy series of films, if we're discussing a hypothetical Warhammer Cinematic Universe.
Let's take Saving Guardsman Rhyan as an example. You have the Only War speech at the start, which describes the Emperor as an undying guide to humanity on the Golden Throne. The audience doesn't know what that means, but it sets up some things. The Emperor is immortal. The Emperor is fed the souls of humans to remain immortal. The Emperor guides humanity.
Later on, we have Guardsmen listening to a sermon, which introduces the phrase The Emperor Protects and establishes that yes, the Guardsmen definitely think of this guy as a god who will save their souls after their inevitable deaths in His service. It shows that the Emperor apparently looks like an imposing, but fairly normal human man through an altar statue. This counters the pondering that if the Emperor eats human souls that he's some kind of inhuman abomination, and shows that the Emperor is something human-esq at the very least.
Later still, we have one of the Guardsmen (the pious one) get shot by a heretic but is saved from death when one fateful stubber round bounces off his Aquila, maybe even ricocheting and killing the shooter. Pious Guardsman gleefully insists that the Emperor saved him, and is all the more dedicated to the mission because it proves saving Rhyan is the Emperor's will. There's nothing physically impossible about what happened; certainly it wouldn't be the first time someone was killed by their own bullet ricocheting...but it is admittedly unlikely in the extreme, and makes one wonder if the Emperor really is watching. For maximum ponder, show Pious Guardsman easily winning at cards no matter how bad the draw, in order to imply from later film's context that he might be a latent psyker.
Once Rhyon has been saved and almost everyone is dead, he and the survivor dedicate them by carving their names into a Shrine of the Emperor's Martyrs. Turns out they were sent to save Rhyon in the first place because he possessed a family heirloom that was of some interest to the Inquisition. It's a little thing, doesn't really seem to have any actual function, and Rhyon lost in in the climactic battle against the heretic baneblade. They're trying to avoid giving the Acolyte the bad news, only for Rhyon to find the thing in his pocket after all, and hands it over. Looming shot of the statue of the Emperor. Credits.
Cmon, be honest here. Dune a) almost exclusively focuses on big characters, nobles, heirs of dynasties. It rarely depicts much of how the common man lives. Half of 40k is built on the misery of the common man and how the Imperium can arbitrarily do what it wants with their lives. Sure it has reasons and decent ones in the context of the universe (heresy = rebellion = chaos = warp rape.) But it really is a celebration of what a totalitarian state can do when it's got the permission of the populace to do so. Or as a friend of mine likes to put it "One guy in a Manufactorum he's worked in his whole life, carving an Imperial Aquila into bolt shell casings under bad light."
But that's not really what 40k is
about, no more than 1984 is about the life and times of proles in Oceania. All that shit is happening, but it isn't really what's important to the story. What's important to the story is fighting aliens, heretics, and traitors. Or finding your way through the political machinations of the Imperium. Or exploration beyond it's borders for profit and more profit. The slavery and dehumanization angle has it's place, but it's as the foundation of a Chaos film.
For example: a shot of people living in an overcrowded, collapsing hab block as a group of space marines walk by. Do you a) play heroic, bracing music as they walk by and look at the most unfortunate of the Imperium's citizens, like these people look up to their saviors as the last line between them and total annihilation....or do you play some sad sack music to show what fighting to save humanity has ultimately done to it. Same scene, to very different interpretations of what they mean just based on the music you cue people with. Do you just omit a scene like that altogether, and sweep the scale of human suffering in the Imperium under the rug?
It all depends on the film's context. In We Were Astartes you play uplifting music and show how much the Space Marines are the heroes of all humanity. In Wolf of Wall Hive you show a sneering noble who believes they know where the real benefits of the Imperium go, to them. And in C for Chaos you play disturbing, angry music as a downtrodden orphan looks on with hate in their eyes.
Interesting maybe. But it can put it up there in the ranks of "why would go I see a movie just to feel bad" kind of things.
A good screen writer could figure all this shit out I think, and understand you need to demonstrate people's willingness to sacrifice for the Imperium as a noble as well as a tragic thing. Because that, heroism and survival are pretty much the only things that are cheer worthy in the dehumanizing, invasive, uncaring and intractable Imperium. A bad screen writer would do it hamfistedly and then maybe put the nail in its coffin by going way overboard on, I dunno, making too much out of a scene where someone get lobotomized and turned into a servitor.
There's a juxtoposition, and from a certain viewpoint it isn't all feelbad. I forget which one it was, but one of the big 40k writers said "In the grim darkness of the far future, there's more than only war. Real people live there too." That's always been the interpretation of the Imperium I liked best. People have found meaningful lives in horrid dictatorships and downtrodden societies. I think that's a part of modern western conceit, that you need democracy and air conditioning to be happy, otherwise everything is shit. Truth is, most people find a way to adapt, and I genuinely think humans could adapt to a society like the Imperium's.
Sure, they're all going to get eaten by Tyranids in the end, but then again we're all actually going to die now. It doesn't mean you can't carve out something in the interim. If praising the Emperor and burning heretics makes you happy, then that's worthwhile. If you can manage a hard-knock life in the Hive, that's worth while. If you can bayonet some fucking Tau bastard to death, laughing as he drenches you in his stupid fucking blue alien blood and spasms in suffering knowing he'll never again see his sick brood of equally damned xenos spawn and their Throne-damned race traitor "Guevessa" allies-
Got away from me there. Point is, there is good in the Imperium. There has to be. You can't have grimdark without it, and yet, from a certain point of view, that also makes grimdark bearable.
Dark Eldar = Independence Day
huh
You know it's true.