Christianity in D&D

In Old Night, I've said that there isn't anything at all like a cleric class. There also isn't anything at all like the pagan mythological pantheons of most D&D settings, which read like shallow rip-offs of Greek or Norse mythology, leavened with some Egyptian or other more exotic ones from time to time. In fact, I once believed and stated that mythological pagan pantheons and the modern fantasy genre seem to go hand in hand. Most fantasy settings had them, and in many cases, interactions of some kind or another with the gods was not unusual. Midkemia did it in the Rift-War (when Pug and Tomas spoke with Lims-Kraga the Death Goddess, for instance) and in the Belgariad, Garion actually ended the series on the finale of fighting and killing Toruk, the evil god of the pantheon; although prior interactions with others were common. Heck, even Tolkien did it somewhat awkwardly; although he never called the Valar gods, and he clearly didn't want to promote anything that would be seen as an idolatrous attempt to supplant God, even in fiction, the Valar did indeed resemble pagan mythological gods in pretty much every sense other than that they acknowledge the superior authority of the One True God above them. D&D settings had often done the same, and familiarity with the Oerthian Greyhawk pantheon goes way back, and the silliness of godly stuff going on in the Forgotten Realms is notorious. 

One of the most overtly "mythological" elements of Middle-earth; when Ulmo appears and speaks to Tuor.

Old Night now has a baseline assumption of true Christianity as the religion that people have in the setting, but then again, I don't intend on making religious activity of any kind of a focus of the game. Much like Tolkien, I don't want to come across as idolatrous, even in fun, nor do I want to explore those kinds of mythological themes. In this regard, I actually seem to be in good company; not only did Tolkien seem a bit leery of embracing them, but so did Gary Gygax and Dave Arneson. Part of this may have been for a different reason; both were Medieval history buffs, and of course, you can't really have European Medieval history make any sense without Christianity to back it up. That is, perhaps, one of the greatest fails of much of fantasy; it tries to mimic a High Medieval society without Christianity, and it falls flat. Had they done an early Medieval setting, where pagans were still relatively commonplace in northern Europe; before the Christianization of the Vikings, the Anglo-Saxons, the Balts and Slavs, etc. it may have worked, but they didn't really try to do that either. In any case, here's some text from an old Grognardia post on the subject. It's not the complete post, but it's a substantial section of it, with a few edits by me. 

[A]s late as Eldritch Wizardry, there are few (if any) explicit references to gods in OD&D. There's much talk of demons, devils, and, tellingly, saints, but gods aren't much talked about until Supplement IV's release in 1976. I once asked Gary Gygax directly about the question of why this was so and he explained that he felt it unseemly to include anything too explicitly Christian in a mere game, even if he assumed a kind of quasi-Christian or crypto-Christian underpinning for the whole thing. This is also why his demons and devils used somewhat obscure names rather than very familiar ones. All the old school love for statting up Satan/Lucifer was something Gary didn't feel was proper. It's the same reason why, even in late AD&D, we get planetars, solars, and devas but never "angels." Interestingly, the original Blackmoor campaign, as I understand it, had a Church, complete with a hierarchy, but no named gods. ... [T]here's an assumption of a quasi-Christianity lurking in the background.

... I know that, in my early days of gaming, my friends and I all tacitly assumed that clerics were Christian priests -- heck, I thought monks were as well -- and that, somewhere, behind all the monsters and magic, the Lord of Hosts was lurking. We never really talked about this assumption or dealt with it in any direct way, but we neither did we question it. It was an odd kind of Christ-less Christianity, more concerned with laying the smackdown on evil than with turning the other cheek or taking up one's cross, except in the most vague of senses. The paladin was an unambiguously Christian knight for us and indeed Lawful Goodness we associated with this unspoken religion that had bishops and cathedrals and holy water and everything else a young boy saw as being "essential" to medieval Christendom.

As time went on and our sense of D&D changed, this implicit Christianity became less important, but it never fully faded away, because it just seemed to us that there was just no other way to look at the cleric and the paladin except in the context of quasi-Christianity. Nowadays, I'm probably too immersed in swords-and-sorcery to fall into this perspective again, but I am now more firmly convinced than ever that early gaming, far from being "pagan," was in fact shot through with Christian belief, practice, and lore. It was always a kind of "fairytale Christianity" broadly consonant with American generic Protestantism rather than anything more muscular, but it was there and it's never really died, even if all the post-1e editions of D&D have tried to varying degrees to remove all evidence of it.