I was asked about the appropriateness of using the word "hell" in a literary work within a world like Lusternia which doesn't have a place called Hell. It's an interesting question and hard to answer briefly.
It's clear that a reference to, say, Microsoft, or Beowulf, or biochemistry, does not belong in a work written and set in Lusternia (the same could be said for most fantasy worlds). In the same vein, a reference to Hell, the uppercase one, is inappropriate. (Of course, you could have a fantasy world that has a Hell in its mythology or as an actual place people visit, but Lusternia doesn't happen to have one; the nearest thing is the plane of Nil.)
However, the word "hell" has become genericized by use, and now has senses which do not allude to that particular bit of our culture. The only connection between the word hell in the phrase "I had a hell of a time" and the Christian concept of Hell is a very indirect connection, one rooted in etymology. (Most idioms started as metaphors or similes, but eventually through repeated use came to mean directly what they had formerly meant only by indirection through that metaphor or simile. Thus, the original metaphor is nothing more than an etymology.)
But in the case of "hell" the etymology is fairly evident. Perhaps it's evident enough to jolt the reader out of any immersion in the fantasy world that she had been able to achieve, and if so, that's enough of a reason to avoid it right there. The question is whether it has been genericized enough that one can read it and get the generic meaning in mind without even a flicker of the etymological original meaning.
Personally, I'd avoid it because while most people would not get the "wrong" meaning and be jolted out, a few people might. However, if it was really the best word to fit the spot and nothing else would do, I might go ahead and use it anyway.
One might say as a matter of principle to never use a word like that. But ultimately, almost every word turns out to be a "word like that" once you dig into its etymology far enough. The difference is that the original meaning is obscure enough that you either don't know it, or only think of it if you make a conscious effort to do so.
And when you get right down to it, every word of English has unshakeable origins in one or another language that never existed in Lusternia; we assume that Lusternians are actually speaking their own language, and it's being translated for us. (Because it's an impossibly ridiculous coincidence to expect that they have a language that actually happens to have the same words in it as English.) So ultimately, even "Hell" might be assumed to be a translation of something that is appropriate in Lusternia.