Helldritch
Hero
Something that is in the core books makes it that it can be referenced by EVERYBODY! Not everyone has the FR campaign books, Eberron, Dragonlance and so one of all editions or current. BUT what everyone have are the Core Books. This mean that while the Great Wheel is explained or more adequately, summerize. It might mean that every table can discuss what THEY DID with it. You might not have Sigil in a campaign in which the DM did not buy that book. Or you might. But one thing is for sure, the great wheel can be discussed by everyone because it is in the core books.Just because something is in the Core Books doesn't mean it isn't setting specific. After all, that section includes a discussion of Sigil, the City of Doors, and the Outlands, along with Gate Towns. And aren't those all details specific to the Planescape setting? And the Great Wheel certainly seems like a setting detail that references specific settings. So does the Elemental Chaos.
Sure, they don't come out and say "in the land of Greyhawk" but that doesn't mean these aren't setting details that are being told to us in the Core Book
The Egyptian Pantheon existed wayyyyyyyyyyyyyyyyyyyyy before the realm. In fact, it was (is) in my own world of Center since 1983... The FR was printed in what? 1987-8? (I don't even care about the date, I know for sure that it was not printed when I started to DM.) The fact that the Egyptian pantheon was incorporated into the Realm does not make it Realm specific. I own a KIA Sorento. It does not mean that only I can own a KIA Sorento. There are better arguments than this...Really? Isn't the Egyptian Pantheon specifically in the Forgotten Realms? I know Tyr from the Norse Pantheon is, and that part of the existence of Oerth in Greyhawk was predicated on the existence of Earth in the DnD world, explaining how these Deities from our history show up in DnD
Ok. You assume that I have Planescape. Do I? Does the next poster have it? Does my daughter has it? You do not know so you can only assume. If I do not own it, I can't verify it. And not all books are available on the net and I strongly recommend people to buy stuff, not download on shady sites...Plus they all showed up in Planescape, another setting.
But If I own it so what? We are discussing core mechanics here. The Planescape box set is not core. What we have in the DMG and the PHB is. That they appear in Planescape does not make them less generic. It makes them part of Planescape. Nothing more, nothing less.
The book gives you examples of what you can do. Nothing more, nothing less.Finally, "you can reference the real world or make up your own" isn't exactly a ringing endorsement for non-setting specific things. Yeah, I know I can homebrew, but the book doesn't provide my homebrewed gods. And I know I can pull things from the real world, so the book providing them doesn't exactly give me anything "non-setting specific" as much as it translates things from the real-world into the DnD world. I could do the same thing with other religions too.
Loki is as core as you want it to be. These were examples. And an example does not make it mandatory. In fact, nothing is mandatory in any core books as you can always homebrew something to better suit your needs. What is evident though, is the fact that Evil gods exists at the core of the books. Doing something else is purely homebrew.So, I think between explicitly referencing other settings or referencing the real world, calling one homebrew and the other "core" is a bit of a stretch. Loki isn't "core" to DnD. Loki is a Norse god that gets called up in dozen of fantasy works, because people like to reference Norse Mythology.