This is going to be subjective, and people are going to disagree from the very beginning about certain definitions, but I am curious how "real" you consider your campaign world to be. It doesn't matter if you use an official 5E setting, a legacy setting, a 3rd party setting or something you designed yourself. I am not really asking about the setting details but how real the world feel when you playing.
What I mean by "real" in this context covers a lot of ground, much of it nebulous. Things like: feeling lived in by whoever populates it; having an ecology even if it isn't a realistic one; same for an economy; does it have religions and cultures and political institutions that make sense in the context of the wider world. Like that.
To reiterate: I am not talking about "realism." I am not even talking about verisimilitude necessarily, although it is related. I am referring to the feeling that the world as a whole operates by rules beyond those that exist to serve it as a game or as a narrative.
Which one?
I love world-building - and if I'm honest, it is more of a primary hobby (or art-form) to me than RPGs, and they essentially exists as two distinct "streams" that sometimes meet (or it could be said that my engagement with world-building creates separate sub-streams, one being stories and the other game settings). It didn't start that way - I discovered D&D and started reading fantasy novels around the same time (early 80s), and world-building was an eventual out-growth of that. But starting in the late 80s, my main or "mythic world" began to separate--eventually completely--from RPGs, and I developed other "game worlds" to play D&D in (as well as still other worlds for other story ideas).
My "mythic world" is (or feels) quite real. It seems to exist in its own right, and I feel less that I am "building" it, as in constructing it from scratch, and more that I am gradually seeing it in greater detail, like putting a puzzle together over many years. In other words, I feel like I'm more the chronicler of a world that exists in its own right that I'm gradually "seeing," and less like an architect of something that doesn't exist until I put pen to paper. So in terms of your question, it definitely feels like it exists outside my conscious awareness.
But I haven't used this mythic world as an RPG setting for maybe three decades. At this point, it is very far removed from anything D&D. In fact, I remember the moment when I realized that the race of beings that I called elves were not actually elves, but something different. This happened a lot, and gradually, over time, the world took on its own life. I
could use it for a D&D setting, but it would essentially require a whole new set of races, classes, and sub-systems and really, when I play D&D, I tend to prefer a relatively "classic" approach, so I've developed D&D settings to use when I DM. This "game world" uses the building blocks of D&D lore and riffs off them, but stays relatively traditional. It doesn't feel as real as my mythic world, but it also doesn't have to. Where the mythic world feels like it could be an actual world out there in the cosmos that I'm "receiving" data on through my imagination, my D&D setting feels more purely constructed - something that I have put together from various elements from D&D canon, various books and other media. In a way it is an attempt to make the archetypal D&D fantasy setting with some personal twists.
Actually, Samuel Taylor Coleridge has a taxonomy of imagination that describes the difference quite well:
The IMAGINATION then, I consider either as primary, or secondary. The primary IMAGINATION I hold to be the living Power and prime Agent of all human Perception, and as a repetition in the finite mind of the eternal act of creation in the infinite I AM. The secondary Imagination I consider as an echo of the former, co-existing with the conscious will, yet still as identical with the primary in the kind of its agency, and differing only in degree, and in the mode of operation. It dissolves, diffuses, dissipates, in order to recreate; or where this process is rendered impossible, yet still at all events it struggles to idealise and unify. It is essentially vital, even as all objects (as objects) are essentially fixed and dead.
FANCY, on the contrary, has no other counters to play with, but fixities and definites. The Fancy is indeed no other than a mode of Memory emancipated from the order of time and space; while it is blended with, and modified by that empirical phenomenon of the will, which we express by the word CHOICE. But equally with the ordinary memory the Fancy must receive all its materials ready made from the law of association.
My mythic world seems to be largely the product of what Coleridge calls
secondary imagination, while my D&D worlds are more the product of
fancy. In fact, there is an ongoing tension in the process of creating the mythic world - I have to constantly keep "fancy" at bay, or rather hear through the noise of its meddling to get at the "signal," if that makes sense. Sometimes I come up with an idea that doesn't feel quite right, and gradually the "true" idea emerges underneath it. It is almost like some ideas start as a "fanciful placeholder" and are eventually replaced with a product of secondary imagination.
On the other hand, my D&D setting is more the product of fancy in that it is intentional built to serve a distinct purpose: to play D&D in. In a way it is much easier, because I don't have to worry about the "true" idea - I just put together bits and pieces that serve the main purpose of the world: to be a setting for D&D game play.
As an aside, I think most RPG worlds are largely the products of fancy, and our common cultural view is that fancy = imagination, and even that Coleridge's secondary (let alone primary) imagination is just a bunch of quasi-mystical woo-woo, even pretentiously elitist. To that I would say, woe is us. In fact, I think this is a limiting factor on a lot of art, and why most film studios and authors (and game designers) tend to just regurgitate and re-skin endlessly.
To quote Seinfeld, not that there's anything wrong with that! A game world is essentially a back-drop for game play. And the setting of a film or book is meant to serve the story. But it does end up feeling like the vast majority of fantasy worlds that are put forth are mostly just re-combinations of already existing bits and pieces, rather than living and breathing worlds that feel like they exist in their own right.
That said, occasionally some film or book or RPG seems to tap into a deeper wellspring, and even worlds built on fancy still sometimes have elements of Coleridge's secondary imagination. To some extent, I think that the degree that a world has its own unique signature and vibe (that is, is
original rather than
derivative), often at least correlates with the degree to which its creator tapped into secondary imagination.
I am
not equating novelty with originality, but that the latter has something to do with something existing outside of the "fixities and definites" of the mind, as if its origin is
elsewhere. Meaning, I'm using "origin" as coming from the depths of imagination - not
derived from pre-existing cultural artifacts.
