Stranger Things is preparing for its fifth and final season, but there are still a couple of mysteries, mostly about the Upside Down, that season 5 needs to solve. The more Stranger Things evolves, the more mysteries pop up about Hawkins, the experiments at Hawkins Lab, and the Upside Down and the monsters living in it, and while season 4 answered some of the series’ biggest questions, there are still many more that need to be solved before the audience has to say goodbye to Hawkins and all its residents – and the most intriguing and important questions are all about the Upside Down.

Stranger Things wasted no time in introducing the Upside Down, an alternate dimension that exists parallel to the human world, and it was presented as a copy of the latter, though in a dark, rotten, decaying environment where no humans lived. Instead, the Upside Down is inhabited by different monsters, most notably humanoid predators known as Demogorgons and a dormant organism the kids refer to as the Mind Flayer. The Upside Down was revealed to be controlled by Henry Creel a.k.a. Vecna, who was banished there by a young Eleven, and while this answered some questions about the Upside Down, there are a couple of big mysteries about it Stranger Things season 5 has to solve – and here they are.

Related: Stranger Things Theory Makes Will’s Link To The Upside Down’s Timeline More Tragic

8 Who Created The Upside Down?

Stranger Things season 4 Upside Down

Since Stranger Things season 1, there have been various theories on who created the Upside Down, the most popular ones suggesting it was either Will Byers or Eleven, but season 4 revealed that the Upside Down has existed since long before the events of the series. When Henry Creel arrived at the Upside Down, he described it as “a realm unspoiled by mankind”, and it was shown as a mountainous and rugged place, with a yellow-brown sky covered with dense clouds. Henry also encountered small Demogorgons, as well as a living organism swirling in the sky that he made into what’s now known as the Mind Flayer. Dustin theorized that the Upside Down has existed for thousands if not millions of years, but how exactly it was created and who is responsible for it remains unknown.

7 Why Does The Upside Down Look Exactly Like Hawkins?

Stranger Things Will Byers in the Upside Down

When the Upside Down was first seen in Stranger Things season 1, it was an exact copy of Hawkins, which made viewers believe that whatever happened in the human world and whatever changes were made to Hawkins were reflected in the Upside Down, but season 4 also debunked this. As mentioned above, the Upside Down was deserted when Henry Creel arrived, and it was just mountains and land covered in strange webs and more, but Stranger Things season 4 didn’t explain why and how this dimension ended up looking exactly like Hawkins. It’s likely that Vecna was the one who turned the Upside Down into a copy of Hawkins, but why would he copy a town that hurt him so much and how he managed to replicate every single detail is unclear.

6 Why Is The Upside Down A Copy Of 1983 Hawkins?

Stranger Things Nancy's diary in the Upside Down

Another big reveal about the Upside Down in Stranger Things season 4 is that this dimension is frozen in time, on a very specific date. When Steve, Nancy, Robin, and Eddie entered the Upside Down, they went to Nancy’s house in the other dimension to stock up on weapons, but when Nancy couldn’t find any of her guns, she found her old diary and realized the Upside Down is frozen on November 6, 1983, the day Will disappeared in season 1. It’s believed this is the day the Upside Down is frozen on because it’s when Eleven opened the gate in season 1, but Eleven had previously opened a gate when she banished Henry and more gates were opened after season 1, yet the Upside Down continues to be a copy of Hawkins on November 6, 1983.

5 What’s Beyond Hawkins’ Limits In The Upside Down?

Stranger Things Hawkins in the Upside Down

One of the biggest mysteries about the Upside Down is how extensive it actually is. When Henry Creel was banished, the Upside Down was an extensive and deserted land, but what’s known and seen so far of this dimension is that it’s an alternate, darker, decaying version of Hawkins, and nothing has been shown beyond those limits. This raises the questions of what’s beyond Hawkins in the Upside Down and if it could be a copy of Earth rather than just of Hawkins, or even be a planet of its own, and it’s somehow linked to the human world. If there are copies of other parts of the world in the Upside Down, that would also raise the question of who created those, as it’s unlikely Vecna’s power could go that far.

4 What’s Eleven’s Connection To The Upside Down?

A bloody Eleven next to a broken room in Stranger Things season 4

The town of Hawkins and even Henry Creel himself wouldn’t know about the Upside Down’s existence if it wasn’t for Eleven. It was young Eleven who managed to overpower Henry Creel at Hawkins Lab and banished him to the Upside Down, though she was unaware of the existence of another dimension and didn’t banish him intentionally, and instead, this was a surprising display of her powers. Before Stranger Things season 4, Eleven was the only one able to open gates to the Upside Down (as Vecna did so in season 4 by killing teenagers across Hawkins), so all this suggests that there’s a connection between Eleven and the Upside Down, though why and how this happened is unknown.

3 What Was The Egg Found In The Upside Down (& What Happened To It)?

Stranger Things Hopper finds a cracked egg in the Upside Down

One Upside Down mystery that Stranger Things has completely forgotten about is the mysterious yellow eggs seen in season 1. When Eleven first made contact with the Demogorgon as part of Dr. Brenner’s experiments at Hawkins Lab, she saw the creature feeding off a yellow egg, and days later, when Joyce and Hopper entered the Upside Down to look for Will, Hopper came across a broken egg near Castle Byers, but it’s unclear what came out from the egg. Stranger Things hasn’t explained what these eggs carry and their place in the Upside Down’s environment, but it’s believed they carry another type of monster yet to be introduced.

2 What Is The Mind Flayer Made Of?

Stranger Things Mind Flayer

The Mind Flayer was introduced in Stranger Things season 2, and it’s a giant spider-like creature with control of the Upside Down through a psychic link, forming a hive mind with the Demogorgons, Demobats, and vines. Stranger Things season 4 showed that the Mind Flayer as it’s known didn’t exist in the Upside Down, and it was Henry Creel who made it into what it now is. Henry explained that among the many things he found in the Upside Down was a living organism made up of swirling, storm-like particles that he described as the “most extraordinary thing of all”. Henry used his powers to form a psychic connection with this mass and shaped it into a giant spider-like creature, like one he once imagined when he was a child. It’s unknown if this mass already possessed consciousness before Henry took control of it or if he was the one who brought it to life, and it’s also unknown exactly what it is made of and what its place in the Upside Down’s flora and fauna really is.

1 Can The Upside Down Be Destroyed?

Stranger things Vecna in the upside down

The Upside Down has become a character of its own in Stranger Things, and its connection to Vecna has made it even more dangerous, more so now that it’s starting to take over Hawkins. One of the biggest questions after the events of season 4 is if the Upside Down can be destroyed and if that can be achieved through Vecna’s defeat given the psychic connection between them. If that’s not the case, the question would be what happens to the Upside Down after Vecna’s death, as even if Eleven closes the gates for good, the other dimension would still be there, with Demogorgons and Demobats and possibly the Mind Flayer as well (if it’s not destroyed along with Vecna). Stranger Things only has one more season to solve all these questions about the Upside Down and many others about Hawkins and the main characters, and hopefully, it will offer as many answers as possible without feeling overstuffed.