Just a concept for environment for boss or extra layer to the game. (Realmatic Transition)

[Illumunaire]

I should probably preface that my idea is not really my own, as the concept originates from Brandon Sanderson's written works surrounding his "Cosmere" universe. But I think it actually really fits DST's atmosphere and general direction with all of the "your insanity is real" and the nightmares that come to life. 

Anyways, I think it would be really cool if there was some way players could shift out of the physical realm and into a sort of nightmare realm. It wouldn't necessarily be like jumping into an entirely different shard like the transition between the surface and the caves, but instead it would be more like transitioning into an overlapping realm to the physical one. The physical realm would become mostly un-interactable and you vanish into a so-called cognitive realm which is a vague reflection of the physical one. What's in the physical realm is now more of a blurry backdrop that you're barely present in, but because you are now in the cognitive realm, a whole other host of objects, flora, and fauna are available to interact with. Nightmare creatures and gestalts from other players are now available to interact with regardless of sanity level, and when near living players, things in the overworld can be haunted or messed around with (but they can't see you or they only see a vague spectre of you).

I have no idea how this could be implemented, if the game mechanics could possibly allow for this (especially with all the invisible, un-interactable objects), or if it's even an appealing idea to anyone. I just think it would be super cool to be able to: 1) Defeat a boss that exists entirely in a sort of nightmare realm kind of like the unseen hands during the Fuelweaver fight, and 2) be able to slightly mess around with other players living in the Physical Realm.