While intending to get his revenge on Eleven and Brenner, Vecna also goes after victims who have dealt with traumatizing experiences in the past (reminiscent of his childhood and his time at the Hawkins lab).
Vecna draws power from sad and angry memories and that is the main reason he targets traumatized teens. Those teens are a well of power just there to be absorbed. This is not just a theory, Vecna himself told Eleven about the power that angry and sad memories hold.
Brenner (Matthew Modine) states in the Stranger Things episode "Papa" that Vecna "consumes" everything about his victims, Vecna targets traumatized victims because it builds for him a well of sad and angry memories to draw from. With each victim, he can become gradually more powerful.
"Vecna seems to be actually intrigued by Nancy being able to figure him out, to be able to get this close to the truth... I think this is more Vecna's narcissistic traits that pull him to Nancy, why he wants to give her this information."
In the real world, he makes the victim levitate while in their trance, before snapping their bones and neck, and crushing their eyes. The murder site then becomes a small gate into the Upside Down, as part of a long term goal to apparently bleed both dimensions into one.
It's probably safer to say that Billy was chosen as the Mind Flayer's first victim because of his fragile state of mind. He was constantly angry, overwhelmed by his abusive father, and became abusive himself in return.
Vecna's obsession with time appears to be linked to his hatred of humanity. He views time as a human imposition on the natural world; an attempt to impose order on nature.
Ultimately, it is revealed in Stranger Things season 4's finale that the reason why Vecna was killing Hawkins teenagers was to create a massive gate that merges the Right Side Up with the Upside Down - and he specifically needed four bodies to do so.
She Doesn't Have a Great Aim
After the Hawkins team develops a plan to defeat Vecna, Nancy is in charge to blow his head up with a shotgun. However, either she didn't have a great aim or she was trying to play it safe because she didn't hit him in the face even once, and that may be the reason why Vecna is still alive.
All those years ago, he felt a connection to Eleven because of their shared abilities and the pain that they had both endured at the hands of Dr. Brenner.
She breaks free, momentarily incapacitates Vecna, and runs with the determination to live toward her friends, dodging debris that Vecna throws in her path. Max hurls herself through the portal, awakes from the trance, and is held by Lucas (Caleb McLaughlin).
Chaiken suggests that while Vecna is a source of horror in Stranger Things, the monster can also serve as a useful vessel for externalizing issues like trauma and depression.
Realizing he had tremendous psychic power, he haunted his family with visions before ultimately killing most of them. His father was framed for the murders and locked away in a mental hospital as a disturbed serial killer. Henry then found himself in the care of Brenner, who decided he wanted more kids like the boy.
Once he takes control of the mind, he traumatizes them by showing the visions of their dark past. He takes them to unknown places and gives them a glimpse of himself. The pain of his victims doesn't end here. Every single one of his victims experiences nose bleeding and severe headaches as well.
What does Vecna want with El? In his twisted mind, Vecna believes that he his helping the world by wiping out humans, as a "predator, but for good." When Vecna asks for El to join him, it's because he also sees her as a predator, "better" than humans.
When One massacres the rest of the children in Hawkins Lab, Eleven banishes him to the Upside Down in the same way she banishes the Demogorgon from season one. One is sent hurtling through the Mind Flayer's lightning and is horribly disfigured, transforming into Vecna.
Instead of escaping Vecna's Mind Lair by hearing her favorite song, Nancy is actually released by Vecna himself. Her freedom comes with a price: He gives her a vision of his plans for Hawkins and tells her to pass that message on to Eleven (Millie Bobby Brown).
Wheeler is Vecna's sister are pretty slim. While it's possible on a theoretical level, it would just be a really weird plot twist, even for Stranger Things. However, it's still odd that Mrs. Wheeler was the only side character with a poster.
After all, Eleven opened a portal to the world before that didn't set off this chain of events. Overall, Vecna has been in the Upside Down for seven years.
Brenner. The episode culminates in Eleven unknowingly freeing One from Brenner's control, allowing him to unleash his true power on the staff and children in the lab, killing everyone except for Eleven and Dr. Brenner, who is only knocked unconscious.
What was Chrissy's Trauma? Chrissy's life appears to be free from flaws on the surface, but in reality, she is struggling terribly to conceal her depression and self-image stemming. She was struggling with these issues, which resulted in her developing an eating disorder due to her mother's verbally abusive comments.
Eleven has a memory during this episode and realizes that 001/Henry Creel (Jamie Campbell Bower) wants her to join him on his evil journey, and she banished him to the Upside Down. 001 then transformed into Vecna, the horrifying Stranger Things villain.
Played by Jamie Campbell Bower, each prosthetic was glued to his skin with medical adhesive by prosthetics designer Barrie Gower and his team. For the finishing touch, Vecna was covered in "glossy slime to make him really, really glossy and wet looking," according to Gower.
This is because his trusted accomplice, Kas the Bloody-Handed, betrayed him and used the sword Vecna created himself to chop off his left hand and remove his left eye. This ultimately destroyed Vecna. Though they're clouded with cataracts, Vecna in Stranger Things has both of his eyes.
Originally appearing in the Greyhawk campaign setting, Vecna was described as a powerful wizard who became a lich. He was eventually destroyed, and his left hand and left eye were the only parts of his body to survive.