Then there's the climatic showdown between Eleven and the monster, which takes place in the show's final episode. As many fans have noticed, she even says, "I am the monster," echoing an idea that Lucas raises at various points in the show. Of course, it's possible that she's speaking metaphorically -- like many science-fiction and fantasy heroes, Eleven is inextricably linked to her nemesis -- but for the purposes of this crazy theory, let's take her comment literally. What if the monster is the Upside Down version of Eleven?
This theory could explain why she disappears into a cloud of ash following the big throw-down: in order for the monster to leave, she must also sacrifice herself. As fans on Reddit have pointed out, the theory would also help explain why Eleven is able to recognize Will and Barb in photos without ever having met them. If true, her powers connect her to the monster because they are, in fact, one and the same. And when Chief Hopper leaves a care package in the woods at the end of the finale, he's not just providing comfort to our favorite Mad Max: Fury Road cosplayer; if the theory is true, he's sustaining the enemy.