Can anyone tell me how Fey & Celestials would regard each other in general? I know Celestials and fiends typically despise each other, as a rule, but I can't seem to find any information on how Celestials and Fey would feel about each other in general. I read somewhere that the Raven Queen and the Prince of Frost have a... Complicated dynamic, but I'm uncertain weather that information is credible, and even if it is, that was a very... unique example. Maybe I'm just not looking hard enough, but I havn't found any information on how Fey and Celestials view each other in general. I know most Celestials usually have good alignments, whereas Fey are more varied with some being cruel, others virtuous, and still more being indifferent or morally ambiguous, but if your average Fey being of say... True Neutral or Neutral Good alignment had a run in with... lets say an angel or similar lesser celestial, how would they interact with each other? Would it be friendly, indifferent, adversarial, or something else entirely? And How do greater Celestials view Archfey? Archfey, at least while in the Feywild, have almost godlike powers. How would most Greater Celestials View that? Would they respect Archfey as equals, fear them as threats to their power, or simply dismiss them as pretenders? What would be the general mood towards Archfey amongst the various Pantheons in D&D?

I honestly don't think you can generalize it as being one feeling across all Fey / Celestials. The Celestial alignment spread includes chaotic as well as lawful individuals (though basically always good); and Fey are mostly chaotic, with a spread across good / neutral / evil. 

There would be Fey of the Unseelie court that probably wouldn't be tolerated by any Celestial, while I'm sure some Celestials would be best friends with upper echelon Fey of good nature. I'd imagine them like a sprawling family tree, where the Fey and Celestials are cousins who sometimes get along, even if they don't "get" one another. 

Oberon and the Archangel Michael meet at a roadside rest stop....

I don't think there's a canonical answer, definitely not in the current edition.  If you want to get sort of cosmological, some would say Celestials and High (or Lower) planes entities would be a bit weirded out by the Feywild and Shsdowfell's existence, as the Upper and Lower planes are oriented toward the Prime Material plane and the Feywild, Shadowfell (and some folks put a dreamlands in there) are Echoplanes of the Prime, but despite the Prime's ties to the planar wheel or whatever, the Feywild and Shadowfell aren't similarly bound.  Forget where I read it, but it pops up a lot in some stuff I've read trying to bring older editions planescapes, so to speak, into 5e.

My guess is individuals from either place will likely come down to a, "“We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow." Or rather the Celestials would likely accept this notion.  The fey would likely be much more mercurial and capricious about it, though well aware of the Celestial stance (and probably think it's funny when they don't think it's stupid.).  

Like ... in general, I'd say celestials and fey regard each other in much the same way as earthlings and martians. Except fey and celestials are infinitely farther apart. It's not like they have youth exchange, culture centers and tourism and so on. I'd say one out of a billion ever met someone of the other type. 

But ... a more widely travelled celestial vs a ditto fey? I'd say celestials consider fey to be rudely frivolous and have childish lack of impulse control, while the fey would consider a celestial a fossilised pile of dinosaur bones, and no fun at all. 

And I'm well aware that there are chaotic celestials - but the above is how I feel it would shake out. The least random fey is infinitely more random than the most random celestial.

Maybe celestials hate fey even more than they hate fiends. Consider the verse in Revelations 3:15-16, "I know your works: you are neither cold nor hot. Would that you are either cold or hot! So, because you are lukewarm, and neither hot nor cold, I will spit you out of my mouth." To them, at least the fiends know they are evil and violently oppose good. Fey don't though, they don't care about what is right and wrong and this could be disgusting to the minds of a celestial. 

There is nothing in the rules as written that I am aware of. My suspicion is that as celestials and fiends are D&D’s representation of the judeo- Christian- Muslim dichotomy of angels and devils/demons while fey are drawn from a non Christian (Celtic more or less) tradition each would generally be wary of the other but willing to deal somewhat with those on same good vs evil alignment as themselves (ie celestials would deal with the seelie court but not the unseelie while finds would do the reverse. 

Quote from Wi1dBi11 >>

There is nothing in the rules as written that I am aware of. My suspicion is that as celestials and fiends are D&D’s representation of the judeo- Christian- Muslim dichotomy of angels and devils/demons while fey are drawn from a non Christian (Celtic more or less) tradition each would generally be wary of the other but willing to deal somewhat with those on same good vs evil alignment as themselves (ie celestials would deal with the seelie court but not the unseelie while finds would do the reverse. 

 True, but I would like to point out that fey were accepted by many ancient Christians as a strange sort of fallen angel that wasn't bad enough to become a demon. Drawing on this, maybe celestials see them as pitiful traitors and fiends see them as weaklings who didn't devote themselves to their cause. 

Quote from The_Summoning_Dark >>

Quote from Wi1dBi11 >>

There is nothing in the rules as written that I am aware of. My suspicion is that as celestials and fiends are D&D’s representation of the judeo- Christian- Muslim dichotomy of angels and devils/demons while fey are drawn from a non Christian (Celtic more or less) tradition each would generally be wary of the other but willing to deal somewhat with those on same good vs evil alignment as themselves (ie celestials would deal with the seelie court but not the unseelie while finds would do the reverse. 

 True, but I would like to point out that fey were accepted by many ancient Christians as a strange sort of fallen angel that wasn't bad enough to become a demon. Drawing on this, maybe celestials see them as pitiful traitors and fiends see them as weaklings who didn't devote themselves to their cause. 

I mean, that's certainly a worldbuilding option, but from the material we have Fey and Celestials/Fiends are on different cosmic wavelengths. Celestials and Fiends are creatures of the Outer Planes, reflections of the big cosmic concepts of Good and Evil. The Feywild, on the other hand, is an Echo of the Material Plane that occupies the same "cosmological space" according to the DMG. And while there's a lot of material on certain varieties/forms of Fey, they don't really break down along axiomatic lines the way Celestials and Fiends do. Honestly, I'd almost say that if Fey don't have the kind of souls that pass on to the Outer Planes, then Celestials and Fiends would only really have regard for them as the Fey's actions pertain to the Material Plane and its denizens, since that's where the stuff that really matters to those two groups is.

For the most part, I'd expect that Fey & Celestials each regard the other as someone else's problem.