The most successful aspect of Stranger Things' marketing is that it's been stacked with clues over the years -- whether it be releasing episode titles in advance or slipping hints into audio and video clips. It's become a treasure hunt of sorts, akin to the 1980s properties like Indiana Jones and The Goonies that the Duffer Brothers love. That hasn't changed with Season 4's first trailer, as fans have already begun to speculate that it contains clues as to the villain's real identity.

The villain is only heard at first, threatening the kids over breaking something -- which seemingly alludes to the Hawkins crew scuppering the plans for the Upside Down's takeover of Earth. The mysterious figure's blue eyes are highlighted in a quick shot, but it comes more into frame toward the trailer's end when it drops from the rafters of a haunted house. It's a man with tentacles and a horrifying face similar to the White Walkers featured in Game of Thrones.

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Max sits at Billy's grave, which reads "Billy Hargrove Mar. 29, 1967 - Jul. 4, 1985 Gone But Not Forgotten."

The Duffers have subsequently confirmed this villain is a take on Vecna from Dungeons & Dragons, but fans were mystified as to how it could speak English. They began to ask if the body was actually a human who was serving as a vessel for Vecna, similar to how Will had previously been possessed. Jumping off from there, many Stranger Things fans have suggested that Vecna could be Billy Hargrove, who died at the end of Season 3.

During Season 3, Billy was controlled by the Mind Flayer and assembled an army of humans who formed the giant Meat Monster that attacked the Starcourt Mall on behalf of the Upside Down. Luckily, Billy would eventually break the manipulation and fight back to help the kids -- including his sister Max. His rebellion came at a price, though, as he was stabbed multiple times and died from his injuries.

Though Joyce and Hopper sealed the Gate and caused the monster to die after Billy's sacrifice, it might be that a grotesque form of Billy somehow awakened and transported to the haunted house in the Upside Down. Since Billy also had blue eyes, that's one clue that he could have been resurrected or otherwise taken over by Vecna.

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Vecna could have chosen Billy due to him being imprinted on in the real world, just like how Will was chosen after he got back home. This would fit with the scene in the Stranger Things Season 4 trailer of Max grieving by her brother's grave, foreshadowing that his story isn't The other much-talked about moment with Max being able to levitate could be Billy's way of giving her powers to fight against this being that is now using him and threatening the people he loves most.

What makes Billy perfect for such a storyline are his emotions. Will had fear and anger inside him, so he was corrupted, and Billy experienced the same feelings. Therefore it's easy to see Vecna wanting to harness his mortal shell and create a rage-filled connection. If Vecna is indeed Billy, that will add an emotional connection between the kids and the villain they're trying to vanquish. It'll also up the emotional stakes for the audience when Season 4 premieres next month, and prove that the Duffer Brothers have once again hidden the truth in plain sight.

Season 4 of Stranger Things premieres on Netflix on May 27.