The Mind Flayer (also known as the Shadow Monster) is the main antagonist of Netflix's Stranger Things franchise.
It is a hive mind for the Demogorgon and the Demodogs, the master of Vecna, the arch-enemy of Will Byers, Eleven and the Party, as well as the ruler from the supernatural world called "The Upside Down." While its proxy form has been killed, the creature still lives within the Upside Down.
Trivia[]
The Mind Flayer was the overarching antagonist of Season 1, the main antagonist of Seasons 2 and 3 and Stranger Things: The First Shadow and a minor antagonist of Season 4.