WARNING: The following article contains major spoilers for Stranger Things: Six #1, from Jody Houser, Edgar Salazar, Keith Champagne, Marissa Louise and Nate Piekos of Blambot.
One of the biggest mysteries in the Stranger Things franchise is just how the Upside Down became aware of Earth's existence. Season 1 hinted it was the U.S. government's MKUltra program that first alerted the dark dimension to its presence, with Dr. Brenner forcing Eleven to make contact with the beings there in the name of national security.
However, Stranger Things: Six reveals the rift may have been opened years before by another test subject; one who may turn out to be just as powerful as Eleven.
While the main series focused on the '80s, this precursor story is centered around the '70s and a young girl named Francine. We find out she has precognitive powers, which Brenner is trying to exploit in order to weaponize her. At home, her dad constantly tests her so as to land Lotto numbers, and this leads to MKUltra upping the ante by having her predict the outcomes of various other scenarios. However, her time as test subject Six pushes her to the limit.
Later on, when Six meets up with Three, aka Ricky, she begins to lose her composure. Although she thought he was her neighbor, Ricky was planted in Hawkins with a fake family, all so the lab could lure in Six and her parents, thus advancing Brenner's ulterior motives. When the truth is laid out, following a heated debate with Ricky, Six is ushered back to her quarters, where she punches her bookshelf in anger. As this happens, a portal opens, and a monstrous hand -- obviously from the Upside Down -- reaches through to try and attack her. She pulls away, and it disappears.
At this point, it seems this is nothing more than a bad vision, and Six thinking she's hallucinating. In the back of her mind, though, given her powers, she's wondering if it could be a premonition. Still, Six downplays everything, as she knows she's fatigued and under severe duress at the facility. At the end of the issue, she sits for lunch with the rest of the test subjects and the hand once more comes through the bookshelf in the now empty room, indicating it wasn't a vision.
It remains to be seen if this rip in the space-time continuum is being subconsciously controlled by Six, or if the creatures on the other side can now tear the fabric open for themselves. Six's powers, as Brenner notes, can be exponentially powerful if harnessed in the correct manner. Like Eleven, Six is stronger than she believes and may unwittingly be opening a gateway to the Upside Down while she's awake. The rift shown in her room seems to be drawing the Upside Down there. It's possible the otherworldly beast is gravitating towards Six's energy or mind, much like with Eleven a decade or so later.
From the monster's grey-hued hands, and the clawed-shape of the fingers, the creature is likely the Demogorgon, though it might have some limitations. Still, this means it's actually Six, and not Eleven, who alerted the Demogorgon to what would go on to become its feeding ground in the Netflix series.
Stranger Things: Six #2 goes on sale June 26.