How do describe this setting?

[Nagog]

Hey ya'll!

So I'm running a game tonight, so if you've got a Gluttonous Wizard and are going to punch Lust in the face tonight, don't continue.

That said, I could use some help figuring out how a setting looks like. So here's the sitch:
In order to access a spiritual plane that thinly layers the Material plane, the party is harnessing a device that allows them to exist one second in the future (only viable within this city). This works because, in this cosmology, the planes are only separated in the present (Imagine all of the planes timelines as a twisted cord, and the present is a comb through with they're all separated). The Futures and Past of the planes are entwined. So how would things look in this combined super-plane?

To further complicate things, this plane is currently cut off from almost all of the known planes. So that could complicate or simplify things, depending.

How would you visually describe this phenomena?

[firelistener]

Sounds like the Ethereal plane to me. The Border Ethereal is what's normally accessible from the Material plane, and is a grayed out and fuzzy-looking plane that mostly mirrors the Material plane. The Deep Ethereal is even foggier and connects through foggy curtains to places like the Feywild and Shadowfell. That sounds more like your "combined super-plane". These are described in more detail on page 48 of the Dungeon Master's Guide if you want to take a closer look at their descriptions.

[Kyutaru]

Sounds like the time compression world of Final Fantasy 8. The sorceress Ultimecia tried to merge the past, present, and future into a single world, one where only she could exist. The effect was a lot of hallucinatory images of people that were and weren't there, places shifting between different time periods, and our hero getting lost in the infinite void at the end of time.