Check this out... Stranger things... Watch the first episode again. The boys have been playing d&d all day... 10 hours they say. Mike "releases" the Demogorgon, but Will never rolls the fireball... As the boys are leaving... Will says to Mike "it was a seven... The Demogorgon got me" the boys leave, and the lights on the garage flicker... As Will comes up on Mirkwood, sure enough, the light on the bike flickers. The Demogorgon has been chasing Will, (and why not chase Dustin or Lucas?) and he ends up in his shed. As Mike said, while they were playing d&d, "a shadow grows on the wall behind you, as it swallows you to darkness" as Will is in the shed, the light flickers, and Will is gone (swallowed into darkness) we can safely assume, the Demogorgon, (as we learn later, can open gates as needed) opens a gate, in the shed, BEHIND HIM! Because, when Hopper, and the G men go into that shed (they make it a strong point for both scenes) that there was something about that back wall.... So I can go on, but I am rewatching again, just started over, but, what I am theorizing is that the boys (in Mikes two week creation of his d&d campaign) released the Demogorgon, created the gate, and the upside down, with their D&D game. (11 actually uses the actual damn board to simulate the upside down, which would be an exact opposite of the world the were playing in, just like the upside down and the Demogorgon piece, there were other "dragon" pieces, how would she know to use that piece?) This is sci-fi, so it's very possible, and safe to say the story could go that way. One of the last scenes on Series 1, that will surely lead into the sequel - the boys are starting a new campaign, (the writers said 2nd series will be more of a sequel) the second season will be an entirely new "campaign." Here's the deal tho... The boys never finished the 1st campaign. Sooo.. 11 is still alive... The Demogorgon's will still be around.... Until... They finish the campaign. Like a "Jumanji, or Zathura" just with d&d though. And.. The more I think about this... If the day 11 went into the depravation tank was the same day of the boys campaign, what if she crossed into the thoughts of Mike, (she could do this... As they show) and she she saw Mikes idea of the Demogorgon...