As somebody who is, let's say, Warhammer 40,000-curious (I played an awful lot of Warhammer Fantasy Battle, Warhammer 40K, Necromunda, Blood Bowl, WHFR etc in my teenage years but have only half kept an eye on GW products since), it has always interested me how the setting sets up but spectacularly fails to deliver on an obvious Christian theological inspiration. We get the trappings of a kind of pastiche, parody or satire of religion in the form of the Emperor. But it's basically shallow and teenage.
This is entirely understandable - since the people who come up with the rules and write the novels are probably mostly themselves agnostics and atheists, and since most of the audience are too. But it has the effect of denuding the setting of what could be a great deal of emotional heft and import - something which I think even non-religious people could appreciate, much as they are able to appreciate the obviously Christian themes within the fiction of, say, Tolkien, Lewis, and Wolfe without having to feel as though they are being preached to.
Sticking with the triumverate of Tolkien, Lewis and Wolfe for a moment then, while clearly Lewis's work was more actively engaged in Christian apologetics than the other two, there is a strong thematic commonality between the three of them in that they all sought to depict fantasy worlds which were very different from our own but which were animated by an idea of divine grace.
This is made very obvious through comparing the work of these authors to their non-Christian or secular equivalents - Ursula Le Guin, say, or ER Eddison, or George RR Martin, or Terry Goodkind, which typically posit a world which is largely defined by human will: the interest is in how individual people or groups amass power, or shape their own futures, or remake society, through their own actions. For Tolkien, Lewis and Wolfe on the other hand, while undoubtedly their stories are characterised by human heroism, that heroism is always reliant for its success on the notion that there is an underlying or overarching (pick your preferred term) natural goodness in the universe which both pulls events towards an ultimate telos and at crucial moments intervenes miraculously in acts of mercy, blessing and so on.
Hence, for example, in The Lion, The Witch and The Wardrobe Edmund is given the chance to become heroic by the fact that Aslan intercedes with the Witch on his behalf to save his life. In The Hobbit Bilbo is able to change the world because of miraculous happenstances (Sting found in a random troll hoard; secret entrances and hidden meanings discovered in maps at opportune moments; stumbling on the ring; the intervention of the eagles and Beorn at the Battle of the Five Armies, etc.). In The Book of the New Sun Severian comes across the Claw of the Conciliator by sheer fluke at the end of the third book. And so on and so forth.
A consistent theme in Wolfe's fiction in particular is the thrusting of a young man into an evidently perverse and dangerous setting (Urth; Mythgarthr; Greece in the aftermath of the Persian invasion; etc.) and the subsequent discovery by that character that he holds a different morality to those around him - rather by 'accident'. And not only this; the character also then discovers that that this personal morality in fact fits into a broader moral structure which underpins the universe, such that the prevailing social order in which he is enmeshed is revealed to be a corruption of what is in fact True. Thus, to take the most obvious example, Severian finds himself by accident (which is to say, grace) stumbling on the awareness that he simply cannot live as a torturer without compunction. And this forces him, over the course of the novels, towards the understanding that the society in which he lives is evil and alien to the proper moral way of things, with explosive results.
The problem that 40K has, as I see it, is that it sets up a kind of metaphysical halfway house in this regard, in positing the perverse and dangerous 'grimdark' setting but hiding away from the counterpoint of natural goodness or right. All of the different factions, including the forces of the Imperium, are basically variations of baddies vying to impose their own conditions of Being on the universe. That's fine, as far as it goes - it works as the setting for a tabletop wargame. But there is something thin and unsatisfying about it when it comes to role playing games - being mere rogues in a 'crapsack world' is only to go with the flow, and going with the flow is not the stuff of good fiction, whether emergent or otherwise.
For events to feel as though they have consequence at the individual level within the context of a setting like that of Warhammer 40K, which is defined by all-or-nothing conflict, they have to be accompanied by the sense that the individuals involved are in some sense wrestling with and against the very conditions of that conflict. I am much more interested in the idea of people in the Warhammer 40K universe trying to do good in terms of a vision of morality that sits entirely at odds with the prevailing morality across the conflicting factions than I am in the basically cosmetic choice of picking between those factions, or the superficial one of glorying in grimdark kitsch. A Warhammer 40K roleplaying game in which the PCs hunt daemons or battle orks is one thing. One in which they try to do good in a different sense is much more appealing.
What I want, I realise I am saying, is for Gene Wolfe to come back from the dead and write Warhammer 40K fiction. Then we would be cooking with gas.