With the Mind Flayer gone, there's an opening for a new baddie in town come season four, and Vecna more than fits the bill. Instead of being a classic-looking monster like the previous villains of the Upside Down, Vecna has a humanoid form along with monstrous tentacles or vines and is responsible for several mysterious murders in Hawkins. His modus operandi involves mentally trapping his victims, feeding off of their pain and trauma, and murdering them in horrific fashion.
As the season progresses, it turns out there's a good reason for his unique physical form and powers. Vecna used to be a human who was subjected to the same experiments Eleven underwent. After committing a massacre in the Hawkins lab, he nearly kills El before she overpowers him and sends him to the Upside Down, where he morphs into his current monstrous form.
