Everything Stranger Things has revealed about the Upside Down so far

polygon.com:

Stranger Things 4 revealed a lot about Eleven’s past and dropped a big twist about who is the true mastermind behind the Upside Down’s war on humanity. But with only one season left to go, we still have a lot of unanswered questions — several of which center around the Upside Down.

In an interview with Variety, Ross Duffer did promise that “answers for the Upside Down is really what the basis of season 5 is about.” But rather than sit around and wait for all to be revealed, we’ve gathered up everything we already know about the Upside Down so we can start making our own predictions.

[Ed. note: The following contains spoilers for Stranger Things 4 part 2.]

The Upside Down is an alternate dimension that mirrors our world — or at least our world if it was a toxic hellscape overrun with creepy, moving vines, filled with murderous creatures linked together in a hive mind system, and is constantly experiencing electrical storms.

Likely because of these storms, the Upside Down affects the electromagnetic field of our world. This is how Will was able to use the Christmas lights to communicate with Joyce and why compasses will, if they’re in close enough range, point to Upside Down gates rather than true north.

When Henry Creel/One/Vecna (who we will hereafter refer to just as Vecna for simplicity’s sake) first entered the Upside Down, the location he arrived at didn’t appear to be a version of Hawkins, though. All we saw was a mountainous landscape and more electrical storms. No houses. No school. No Castle Byers.

But if the Upside Down didn’t always mirror Hawkins, is it truly a parallel dimension that reflects our world or an alternate dimension that was transformed to reflect our world? Or maybe it’s simply that the Upside