The Dark Dimension is a parallel spatial dimension that coexists with our own. It strongly resembles the corresponding locations in Hawkins, Indiana. The parallel dimension is also referred to as Vale of Shadows by Dustin, Lucas and Mike, strongly influenced by Dungeons & Dragons game table. The description read by Dustin says as follows:
The Vale of Shadows is a dimension that is a dark reflection, or echo, of our world. It is a place of decay and death, a plane out of phase, in [place] with monsters. It is right next to you and you do not even see it.
The dark dimension is dimly lit, with ropy, root-like veins growing over many surfaces. The air is filled with what appear to be feathery spores. The only "living" entity is the Monster.
Portal to the Dark Dimension
A doorway between different dimensions is a chaotic cleft between space and time that causes significant side effects, with disturbances in the magnetic field and cataclysms being but few. A doorway to the Upside Down is a split of the consistency of tar or a black jelly that seems to have its own life and tends to close behind unfortunates who pass through it.
When the kids ask for explanations to Mr. Clarke regarding different dimensions, he explains that inter-dimensional travel is not possible because humans are not capable of creating the massive amount of energy needed. Theoretically, however, you would have to create a tear in space and time, then create a gate to allow passage. Eleven's psychic abilities enable her to easily reach the Dimension, but anyone can be swallowed by a gate and find themselves lost in the Upside Down.
- Anyone can affect the real world through electricity through the dark dimension. Will exploited this to communicate to his mother from the alternate version of his own house. Voices can also be heard, albeit not clearly, from either the dark and the real world.
- The creature is able to pull individuals (like Will and Barbara Holland) into the dark dimension, and can briefly enter Hawkins through tears in space time. This creates a spatial distortion similar to a wall bending outward and eventually ripping open. While many of the tears have mended themselves, there exists one that has remained and is the largest tear and nicknamed "the gate".
- El's power was strong enough to rip apart space-time and create a gate to the dark dimension, which is why she later blamed herself as the creature took advantage of it to feed off humans.
- The way that one of the lab employees penetrates through a doorway reminiscent of a similar scene in the movie Poltergeist.
- Here’s Ross Duffer describing the unexplored mythology they’re holding in reserve for the next season of Stranger Things:
With the Upside Down, we have a 30-page document that is pretty intricate in terms of what it all means, and where this monster actually came from, and why aren’t there more monsters — we have all this stuff that we just didn’t have time for, or we didn’t feel like we needed to get into in season one, because of the main tension of Will. We have that whole other world that we haven’t fully explored in this season, and that was very purposeful.
- Matt said:
We wanted a simple drive and a somewhat simple mystery with bizarre pops of supernatural horror and then add a larger mythology behind this rift that we only know and refer to as the Upside Down because that’s what the boys decide to call it. They’re theorizing based on their knowledge from fantasy gaming and their science teacher, Mr. Clarke. That’s as much as we get to understand it.
- Ross said:
If there was going to be a season two, we would reveal more of that 30 page document, but we’d still want to keep it from the point of view of our original characters. It sounds like a big part of their 30-page mythology document deals with the nature of the Upside Down, suggesting the parallel universe will also play a big part in a theoreticalStranger Things Season 2.
- Ross explained some of the consequences that might spin out of Will’s time in the Upside Down:
Will’s been there for an entire week, and it’s had some kind of effect on him, both emotionally and perhaps physically. The idea is he’s escaped this nightmare place, but has he really? That’s a place we wanted to go and potentially explore in season two. What effect does living in there for a week have on him? And what has been done to him? It’s not good, obviously.