Vecna

Vecna is a monster in the Upside Down who is waging war agaiinst Hawkins. Prior to his transformation he was Henry Creel, a misantrophic boy who discovered that he had telekinetic abilities and preceeded to murder his own family. He was subsequently taken into Dr. Brenner's care and became the first in Hawkins Lab's experiments on children with superpowers.

In 1979, he wiped out the other test subjects. In a duel with Eleven, he was banished to the Upside Down and transformed into his monstrous form. He used the Mind Flayer to infiltrate Hawkins two years in a row, before fiinally succeeding in opening a gate between the dimensions in 1986.