For much of the show’s run, the Hawkins Lab’s first test subject is thought to be dead, but his psychokinetic powers serve as the inspiration for all the abilities Dr. Brenner develops in his young charges. However, part one of “Stranger Things” season 4 concludes with the shocking reveal that One (Jamie Campbell Bower) is still alive. He was formerly a boy named Henry Creel (Raphael Luce), who went on to work as an orderly in the Lab. He also has the ability to change the perceptions of those around him, and uses this gift to torture and kill his family, crimes that serve as the catalyst for Dr. Brenner’s experiments.
At first, One befriends Eleven and convinces her to remove an inhibitor device implanted in his skin. With his powers unleashed, he massacres the lab’s other subjects, and has a showdown with Eleven in the ruined rainbow room. Eleven eventually gets the better of One and dispatches him to the Upside Down, but his regenerative powers come in handy in that harsh environment. Eventually, One transforms into the terrifying monster known as Vecna and connects with the Mind Flayer. Time will tell if these beings are actually one and the same, but this powerful partnership will likely dominate the fifth and final season of “Stranger Things.”
Using a technique that Dustin (Gaten Matarazzo) dubs Vecna’s Curse, the former human seeks out troubled victims and exploits their past traumas. Once he has located his prey, Vecna’s targets suffer from headaches, and soon begin to see visions that play directly into their negative intrusive thoughts, mentally torturing themselves with their own guilt and shame. In the final stage of this torment, Vecna destroys his victims’ physical bodies, breaking their bones and gouging out their eyes. Each death creates another portal between worlds, four of which will give Vecna unprecedented power over Hawkins.