okay, not even gonna touch the other one but here's for blind eternities.
First things first. WotC buys TSR in 1997. Despite the fact that Magic is starting to kick off, DnD still has the backing of two editions of lore. Where this comes into being is a nice module set called Spelljammer. This is the oh look we travel between the worlds modules. Pretty much (while my knowledge is limited) the dnd worlds were in a multiversal cluster crystal that you could travel between with the correct ship and such. Apparently even if the modules haven't been updated every so often an old spelljammer ship shows up somewhere in the editions.
Now, if WotC really decides to drag the mtg multiverse into this there's a really easy fix. That crystal? someone's pet project to allow a set of clustered planes to travel between each other. And the Mending screwed it up like all other forms of non planeswalker travel which is why no spelljammer anymore. That said this second part is theoretical. Please don't quote me
I got into D&D too late for Spelljammer, but basically it was "D&D IN SPACE!" with each solar system inside its own crystal sphere, and some sort of void between the spheres that the Spelljammer ships could traverse. there was some stuff in the void between the spheres that I can't remember the name of, but it had a current, and the ships (basic wooden sailing ships or whatever) can sail along the currents of the aether or whatever it was, between Spheres, allowing someone from, say, Greyhawk to visit Toril and vice versa. And there were all sorts of gribbly nasties out there too, like mind flayers in giant octopus ships and the like. It sounded great, from what I read about it, but because it was for an earlier version of D&D, I never really got into it.
Sigh. v.v Missed opportunities. At least D&D had ways to cross between various Prime Material Planes (the various D&D worlds), such as going through the Deep Shadow, or finding the World Serpent Inn. Be careful around that one, by the way, sometimes the kender get loose. >.>
As for the Blind Eternities, I would like to direct your attention to D&D's "Far Realm". They sound very similar. A realm outside the usual multiverse, within which all the Planes of Existence reside, a place where thought and reality grow ever intertwined, and vast city-sized beings occupy dozens, hundreds, or thousands of different layers at once, and the layers of reality grow thin and translucent, allowing one to see from one layer to the next, growing ever more indistinct with distance, as in the far background, sourceless lights illuminate mad geometries in true Lovecraftian style, and the tides of insanity wash away all reason.
Why are you leaving tabs open all the time? When there are a lot of things I want to look at, I bookmark them whenever possible... For what purpose do you keep all those tabs open?
