: Eleven's "mentor" in the lab is revealed to be 001 , the powerful first subject of Dr. Brenner's experiments.

: Eleven defeats 001 by pushing him through a portal into the Upside Down , where the dimension’s environment transforms him into the monstrous Vecna . Why It Is Highly Rated

The "good feature" or massive plot twist in , " The Massacre at Hawkins Lab ," is the revelation that Henry Creel (Victor Creel’s son), Number One (the first child experiment), and Vecna are all the same person. The Triple Reveal