In Stranger Things Season 3, the Spider Monster, also known as the Mind Flayer, emerged in the summer of 1985. This terrifying creature made its residence at the Brimborn Steel Works in Hawkins, Indiana. The Mind Flayer, through its flesh thralls and the Flayed, gathered strength and began its reign of terror. This event marked a significant turning point in the series, introducing a new level of horror and suspense.