Batman wrote: ↑2023-03-16 08:22pm
'Within' setting canons I am aware of. I didn't know there was an OVERALL one.
They kinda have had since second edition. Planescape and Spelljammer were both exercises in explaining how characters can get from the Realms to Krynn or Grayhawk or Mystara (you can go through portals in the city of Sigil, or you can hop aboard a spelljammer and fly through space to get there), and when they expanded Ravenloft into an entire larger setting, they used the mists as an excuse to give it crossover aspects as well; the mists can appear on any world and take player characters to the domains of dread, allowing any party composition you want. Among the many beings trapped there besides Strahd, you also had Lord Soth from Dragonlance, at least until an adventure path set him free to return to Krynn. Spelljammer was also used to help explain how Tahkisis was able to steal Krynn away from the other gods for a brief period of time: she literally moved the solar system away from where it was, and I guess that's all it took to confuse the other gods. The lich Vecna also started life on one world (Grayhawk, I believe), before his machinations moved him to full deity and effecting not just the Grawhawk pantheon, but the Realms as well.
Of course, this always ran into problems, and those problems had a name-- Dark Sun. Dark Sun wasn't supposed to be a D&D product originally, the designers wanted it to be a standalone wargame, but the idiots in charge of TSR insisted that it wouldn't sell if it didn't have the D&D branding on it and rules for using it as a campaign setting. The problem was that Dark Sun's themes were post-apocalyptic (inspired in part by Barsoom), and so the question was if its so easy to jump on a spelljammer and leave a world behind, why hasn't Athas been completely evacuated already? So they had to make up excuses for why Athas was inaccessible by either of the established world hopping methods that they had created. This wasn't just a thematic problem either, you didn't want a Darksun character appearing in Ravenloft because Darksun had its own rules allowing characters to be much higher power level for level than normal D&D characters. Not only did the setting make it easier to get psionic powers, they used a different method for determining their stats, which allowed them to have greater than average ability scores. This was fine as long as you played these characters
on Darksun, because the setting had unforgiving survival rules, class restrictions, healing was hard to come by, and equipment was deliberately kneecapped. But as soon as you let a Darksun character leave the setting, none of those things were applicable anymore, and your class balance was screwed. It really was a completely different game, despite the branding, but corporate couldn't be argued with.
Also, they really kinda went overboard making two different campaign settings just to justify adventurers going to and from Grayhawk and Krynn or wherever else they came from, and ultimately people remember Spelljammer and Planescape more for being their own settings rather than being transitional settings like was intended. They put a lot of work into them, when they could have just designated the shadow plane or something as the part of the cosmology you go through to go from world A to world B (which was what they suggested in third edition instead). Still, it seems Wizards today has a different opinion of how to handle these things in 2023 than they did in 1999, because not only did they resurrect Spelljammer, they are currently working on Planescape, and even introduced a new piece of lore (which some people hate) that all the settings originate from one sort of platonic ideal setting known only as the "First World", so that they can say that certain deities like Tiamat and Takhisis (which are both evil hydras with all five chromatic dragon heads) are actually the same god (you can imagine how much this pisses off Dragonlance fans in particular). So they want to have their cake and eat it too again. Spelljammer has been modified so that now instead of having crystal spheres and phlogiston (which people just found weird), its part of the Astral plane. This might also make it clash less with Planescape. No more Darksun, though not because it clashes with the rest of the game-- at least, the claim is that its content is too "problematic" for the company to feel comfortable updating it in 2023. Pretty much everyone assumes they're talking about all the slavery and genocide that is part and parcel of Dark Sun, and that even if they could fix it, they don't want to open it up for DM's guild and provoke fans of Gor or whatever to start posting that and worse in the guild. I actually can't say I blame them.
But yeah, that's how the various worlds of D&D have been canonically connected in second edition, took a break from that in third and fourth, and are returning to a multiverse in fifth.
However, confusing things is that Wildmount/Exandria is still the copyright of Matt Mercer and Amazon, and they've made statements exempting the three Magic: the Gathering worlds that they have published D&D setting books for, because Magic already has its own multiverse.