The reason why Eleven is utilising her powers likely has to do with the stranger thing in the centre of the poster: a monster we have yet to name, but certainly looks as vicious as any Demogorgon. Is this monster the reason why all the rats at the bottom of the poster look, well, very dead? Maybe — or maybe it has to do with whatever factor that bad boy Billy is standing in front of. Could it be a shell business for something more sinister, a la the power plant in Hawkins? And what of the man standing to the left of the poster? It’s difficult to tell what he’s holding, but he looks quite intimidating.