Henry Creel, also known as One (001), or Vecna, is the secondary antagonist of the Stranger Things franchise.
He is the estranged son of Victor and Virginia Creel, and the younger brother of Alice Creel, who gained psychic powers after traveling to Dimension X. Growing up to be a test subject of Dr. Martin Brenner and become an emissary for the Mind Flayer.
After being banished to the Upside Down, Vecna goes on a murder spree in the town of Hawkins in order to start release his master from the Upside Down and start a full-blown invasion of Earth. He is also the former friend/mentor turned archenemy of Eleven and Max, and Dr. Brenner's first subject.