In the D&D realm, a defining feature of Vecna is that he's missing his left hand and left eye. 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.
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.
What Does Vecna Want? Vecna's goal is to open as many gates to the Upside Down as he can, in order to help the Mind Flayer.
Patrick was targeted due to his father's abuse of him. Finally, Vecna targets Max for her trauma from witnessing Billy's death and uses Barb's (Shannon Purser) death as a way to use Nancy.
Season 4's main villain Vecna contains a multitude of easter eggs. To start, he has a giant, claw-like left hand. This is a reference to the D&D character Vecna, for whom this Vecna is named; the D&D Vecna has a monstrous hand infused with dark magic.
As Vecna, he uses these mental abilities as a way to psychologically weaken and lure in his victims – much in a way that Pennywise, Freddie Kruger, and Pinhead do. (All of which have been cited by show creators the Duffer brothers as inspirations for the villain.) But he does have a surprising weakness: music.
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.
Turns out, he needs exactly four dead kids, like the four chimes of his signature clock, as they are his necessary sacrifices in order to open enough small gates in Hawkins, so that he can create that earth-shattering gate in the final episode.
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.
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.
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.
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.
Original Dungeons & Dragons
The name Vecna was an anagram of Vance, the surname of Jack Vance, the fantasy author whose works inspired the magic system used in Dungeons & Dragons.
Seeing Stranger Things' Vecna Made Millie Bobby Brown Cry
She's a 10, but she cries when she sees Vecna? She's an Eleven.
Though they're clouded with cataracts, Vecna in Stranger Things has both of his eyes.
The fan-favorite character ended the season in a coma with her bones broken and eyes blinded at the hands of Vecna. Max technically died for one whole minute before Eleven revived her friend, but Eleven's powers weren't enough to bring Max fully back to life.
Vecna as a Means for Externalizing Trauma and Depression
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.
Vecna feeds off his victims' trauma and haunts them with their own darkest thoughts.
Vecna's use of his victims' guilty conscious to terrorize his prey is an obvious tool in his arsenal. What is more subtle and powerful is that he uses shame to isolate and control. All of his victims, starting with Henry's father, believe that if people know the truth about them, they will face rejection.
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).
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.
Well, in one of the previous episodes, it was revealed that with each person Vecna kills, he creates an opening to the real world. And with Chrissy, Fred, and Patrick McKinney already being his victims, he is just one kill away from creating the fourth portal.
His first victim was Chrissy Cunningham. Vecna targeted Chrissy by using her depression and eating disorder against her in his visions. Chrissy was killed in Eddie Munson's trailer, and the first gate was opened on the ceiling.
Jamie Campbell Bower wore a costume and prosthetics to transform into Vecna in "Stranger Things." The actor said that his suit had a "flap" that went over his crotch.
The first image Gower shared was of the makeup test for Vecna where he confirmed that is indeed actor Jamie Campbell Bower under that scary face.