Theoretical inter-setting interactions.

[Promethean]

Considering the plethora of ways D&D's different settings can potentially interact with each other(World serpent inn, Spelljammer, Planescape, Gig-adventurers in Ravenloft, etc.), there are a lot of weird ways for them to potentially interact.
What are some that have been living rent free in your head?


For example: What do you think would happen if an terminally insane High-Level Wizard tossed an elder evil into ravenloft(likely shortly before their own demise by vengeful Dark Powers)?

Thinking about it, everything inherently "Evil" gains an immense power-boost in raveloft. Hags, Lycanthropes, evil fey, Liches/vampires/(really undead in general, the dark powers have a Serious necromancy fetish) get a bunch of ability boosts, more/better resistances, and a host of new salient abilities. Even lesser fiends thrown into ravenloft get such a power-boost from the effects of evil on the plane that they twist reality over a couple miles and can pretty much ignore planar boarders. In normal worlds, most of the above easily become jokes to even un-optimized parties of middling level, but in ravenloft they're nightmare-inducing threats.
Comparatively, even the puniest weakling of the Elder Evils(zargon) Passively alters the weather patterns of entire planes just by waking up and can actively severe the connection to the gods in a hundred miles(and the gods can't do anything about that until zargon is dead).
The effects would be something to behold.

[Tzardok]

A fiend's reality wrinkle (incidentally, Celestials also get one) is the result of the pressure concentrated alignment puts on Ravenloft's fragile planar structure. It's why the dark powers prefer fiends to either do power rites, thereby incorporating themselves into the demiplane, or to expell them. For that reason I'd imagine that the dark powers are extra vigilant regarding shenanigans like that and would work to either bar the elder evil's entry or bind it into a harmless position as a darklord (see also Gwydion, the Sorcerer-Fiend).
Incidentally, if I remember correctly an elder evil's sign is specifically the effect of its nearing on the Material, which means that it wouldn't have a sign on other planes like Ravenloft, ironically rendering it less scary.

May I suggest afroakuma's Planar and Other Oddities Questions Thread (https://forums.giantitp.com/showthread.php?616081-afroakuma-s-Planar-And-Other-Oddities-Questions-Thread-VIII) for further questions in that direction? We specialize in interactions like this.

[Analytica]

Presumably the Ravenloft Dark Powers _are_ an Elder Evil?

[Tzardok]

With the Dark Powers you never know for sure, but... probably not?

This is made more complicated by the fact that elder evil has different meanings in D&D. "Elder evil" in the context of Forgotten Realms are apocalyptic creatures with prophecies about them, like Kezef, the Chaos-Hound or Dendar, the Night-Serpent. Under that definition the Dark Powers are unlikely to be elder evils, as they are not connected to the setting and generally unknown. The "elder evils" of Lords of Madness are entities from the Far Realms that are revered by the aboleth. Under that definition the Dark Powers are probably also not elder evils; Ravenloft is too comprehensible in its being to be Far Realms related. Finally there are "Elder Evils" as in the book Elder Evils, which are designed to be large-scale threats designed to be the focus and final boss of a campaign. These Elder Evils don't really have a lot to do with each other and include amongst others a group of aliens, a stillborn god, a demon lord, an ancient chaos-monster, a god-slayer from beyond the multiverse and a horny ooze-monster. The Dark Powers are, again, unlikely to be an Elder Evil by that definition, as they are not intended to be a final boss (or an opponent in general).

I always say "unlikely" and "probably not" because the Dark Powers are fundamentally a giant question mark. We don't know what they are. We don't know how many there are or where they come from. We can only guess their abilities and limitations from what they've done and not done. We don't even know their intentions. Are they on the side of Good or Evil? Is Ravenloft a prison for vile monsters, with the innocents there unfortunate collateral damage? Is Ravenloft an amusement park, where monstrous villains hunt innocent victims for the creators' enjoyment? Is it for rehabilitation? Is it just a cosmic joke? We don't know.

[Morphic tide]

While not quite "inter-setting", Ghostwalk has some pretty interesting potential for technically setting-agnostic subsystem sourcebooks.

With Psionics, you have a completely separate use of "Ectoplasm" associated with the Astral Plane instead of the Ethereal. This gives a clear reason to need some specialized training to affect Ghosts in full despite theoretical overlap in what's being used, and a case for escaping the Ethereal Current by moving to a different source of Ectoplasm, resulting in an Unbodied/Uncarnate status that is MUCH more Lich-like, with a bonus of not being on the Prime Material by operational necessity.

The premise of Incarnum as soul-power gives a good reason for outright transparency mechanics (perhaps aimed at Soulborn's extra feats?) to juice up Ghost abilities with one's living-class, and Ghostwalk-Ghosts not being Undead averts the crippling mechanical trouble this natural combination of "soul-power subsystem" and "disembodied soul template" would normally suffer. Fragmentary impressions of souls for Soulmeld basis, by the extant examples of Soulmelds, are easily filed under "why other Types don't get Proper Ghosts", and give an alternate mode of corporealization that can futz with The Calling, for a much "cleaner" route to a majority-Ghost character that's not entirely separated from the Ethereal Current.

For Tome of Magic, there's the obvious of Vestiges for True Death'd beings of importance and applying Pacts to mess with The Calling. With Named Weapons you have a touchstone for a few new "good but not exploit-bait" Crafted Tool utterances, and the premise gives decent grounds for a substitute Lexicon to remove the borked Evolving Mind DC scaling. Shadowcaster doesn't have an OBVIOUS interaction, though the Shadow monster(s) interaction could be promising and Shadow-stuff as a(nother) substitute for Ectoplasm could have neat applications.

[Inevitability]

Faerun is, ultimately, about the antics of gods trying to maximize their number of mortal worshippers.

So what if creation forges showed up there? In eberron, their capabilities are mostly limited by lack of available worked raw materials. In faerun, where 'an epic-level wizard conjured a mountain of mithril' is a plausible plot point, that's much less of an issue.

I don't know exactly what easily mass-produced ensouled beings would do to the setting, but I could see a lot of gods switching their usual schemes over to 'how do I create as many loyal warforged as quickly as possible'.

[Morphic tide]

Faerun is, ultimately, about the antics of gods trying to maximize their number of mortal worshippers.

So what if creation forges showed up there? In eberron, their capabilities are mostly limited by lack of available worked raw materials. In faerun, where 'an epic-level wizard conjured a mountain of mithril' is a plausible plot point, that's much less of an issue.

I don't know exactly what easily mass-produced ensouled beings would do to the setting, but I could see a lot of gods switching their usual schemes over to 'how do I create as many loyal warforged as quickly as possible'.
Given the total lack of recalling an afterlife, Warforged seem to have something about them that makes for poor petitioners, which is an essential part of how gods get power from worshippers as it's the source-material for servants. The best-case scenario is that the Creation Forge is "spiritually upcycling" Livewood, but not all the magical treatments follow the soul after death. In which case Warforged petitioners would be insentient sculptures, possibly only correlating to the Livewood components.

Additionally, a lot of the antics of Faerun deities are about getting the right kind of worshipper well beyond the remit of the False rather than maximizing raw number, such as Lolth's social engineering absurdities. In this case, even if Warforged make for viable living worshippers and usable petitioners, plenty of them would pass because they just don't like Warforged. In the "enriched Livewood" case you'd almost definitely see a counterintuitive adoption by a Nature or Agriculture deity as the soul is that of a plant.

[Telonius]

Athas and Faerun. How a dead-gods setting would interact with the Wall of the Faithless has been tumbling around in my head for a long time.

[Tzardok]

Athas and Faerun. How a dead-gods setting would interact with the Wall of the Faithless has been tumbling around in my head for a long time.

Isn't that Athas on its own already? Athas has the Grey, and like 99% percent of all souls in Athas get stuck in the Grey on their way out to either become incorporeal undead or rot away over the centuries.

Now, if the gods of Faerûn were to suddenly die today, I'd think the Wall of the Faithless would stop mattering as it is not intrinsic to the setting but instead the work of the God of Death. Back when Jergal was god of death, the Wall didn't exist yet. Myrkul built it because he had no idea what to do with the atheist souls that kept piling up in his realm, Cyric kept it because he enjoyed people suffering, and Kelemvor tore it down (before 3.x retconed it back into existence for no discernible reason).

[Prime32]

Given the total lack of recalling an afterlife, Warforged seem to have something about them that makes for poor petitioners, which is an essential part of how gods get power from worshippers as it's the source-material for servants. The best-case scenario is that the Creation Forge is "spiritually upcycling" Livewood, but not all the magical treatments follow the soul after death. In which case Warforged petitioners would be insentient sculptures, possibly only correlating to the Livewood components.

Additionally, a lot of the antics of Faerun deities are about getting the right kind of worshipper well beyond the remit of the False rather than maximizing raw number, such as Lolth's social engineering absurdities. In this case, even if Warforged make for viable living worshippers and usable petitioners, plenty of them would pass because they just don't like Warforged. In the "enriched Livewood" case you'd almost definitely see a counterintuitive adoption by a Nature or Agriculture deity as the soul is that of a plant.
There's a few possible explanations for where warforged souls come from.

The Godforged believe that they're all fragments of a paradoxical "disembodied construct" called Primus The Becoming God.

Some fringe scholars identify The Becoming God with the Silver Flame (note that Flamists can actually get an alternative afterlife by melding their souls with the Flame). Some slightly more mainstream scholars believe that the Silver Flame always existed, with the sacrifice of the dragons and coautls merely summoning it into their reality.

Some ancient warforged were created as quori host bodies, so it's possible that the modern variety are some kind of weird kalashtar, maybe based on Taratai (the kalashtar's original leader, presumed dead).



Also, Volo would probably love Eberron. Something about freedom of the press and open-sourcing magic.

[Inevitability]

Also, the idea of a single one of faerun's epic-level NPCs getting dropped into eberron would be kind of funny.

The dragons would band together to pull off an assassination eventually, but given that the giants used enough magic to up a moon and the dragons still didn't quite think that warranted intervention, things could get pretty crazy in the meantime.

(what provoked the dragons wasn't the giants severing Dal Quor - it was the giants threatening to use that level of magic on an issue that the dragons simply didn't care about)

[Prime32]

Also, the idea of a single one of faerun's epic-level NPCs getting dropped into eberron would be kind of funny.
There are some things in Eberron powerful enough to threaten even a setting as high-powered as Faerun if they got loose. Leaving aside vaguely-defined stuff like Transcendant Dragonmarks, Quori Monoliths and whatever created the Mournland, the Overlords are essentially a pantheon of Rank 7 deities with the serial numbers filed off, who have tight enough holds on their portfolios that they could potentially power up by challenging Faerun's native gods.

While it would be difficult for, say, Sul Khatesh to actually kill a greater deity like Mystra in a fair fight (never mind how many other people seem to manage it), she's actually 5 levels higher than Mystra and a better raw wizard once the divine bonuses are put aside. So if Mystra died again, she'd probably make a viable candidate to replace her.

Also notable is that the Silver Flame is implicitly capable of bypassing a deity's defences against being magically imprisoned.