Music evokes strong memories that are both good and bad, so it makes sense that it could open a doorway out of the oppressive alienation of trauma, despair, and guilt that Max found herself in.
During the episode, Nancy and Robin learn that music is the only thing that can save people from Vecna's wrath. This bit of information proves useful as the gang is able to fend of the upside down demon and save Max using her favorite song Kate Bush's 1985 hit "Running Up That Hill (A Deal with God)."
If Vecna has you in a trance, listening to your favorite song can help pull you out of it, as we saw when Vecna attacked Max only for her friends to pull her out his trance using the synth-tastic stylings of Kate Bush, specifically her 1985 hit “Running Up That Hill (A Deal with God).”
“Music can remind people of who they are, of who they love, of their past. So sharing a musical experience can help them feel connected again to the present”—which is how the characters of Stranger Things successfully use the song.
After learning how Victor Creel was able to evade death back in 1959, Robin and Nancy deduce that playing the victim's favorite song can help them escape the trance that Vecna places them in, with music and happy memories being the only way to keep Vecna's fatal curse at bay.
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.
He is terrifying because he has access to secrets and the guilt that accompanies those secrets. Vecna's use of his victims' guilty conscious to terrorize his prey is an obvious tool in his arsenal.
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). "I thought we lost you," he cries. "I'm still here.
"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."
Max rises into the sky, her limbs begin to snap, and she goes blind. Max briefly dies and the portal begins to open to The Upside Down, but Eleven throws a monkey wrench in Vecna's plan by bringing Max back to life.
These visions build over time, and within a space of 24 hours Vecna's victims enter one final trance. There, Vecna taunts them, rejoicing in their heartache and sorrow, before killing them. Vecna's victims die in an agonizing way, lifted high into the air.
This is when the gang discovers that the only way to save her by his curse is to play Max her favourite song. The gang then plays “Running Up That Hill (A Deal With God)" by Kate Bush, which helps in saving Max's life.
After a certain period of time, Vecna will finally kill the victim by placing them into a comatose-like state, in which they will be unable to respond to outside stimuli.
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.
For Vecna's voice, Henighan says they took Campbell Bower's performance and manipulated his voice so that “the clarity, the strength and the power was there. …
He used his powers to reconstitute the mist-organism into a form that satisfied him: a giant, spider-like entity with a flame-shaped head. In time, this entity would become known as the Mind Flayer. With the Mind Flayer at his side, Vecna's powers greatly expanded.
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).
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.
Vecna holds off Eleven long enough to brutally attack Max in his signature style—she levitates, her eyes go white and bleed, and he snaps her limbs. Eleven regains her strength and pushes Vecna off before he can complete the job, but the damage is already done.
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.
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.
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.
Vecna feeds off his victims' trauma and haunts them with their own darkest thoughts.
Despite his Pure Evil status, Vecna's actor, Jamie Campbell Bower, stated that he sympathizes with his character, as he believes he snapped due to feeling disenfranchised by society and that he did have some genuine care for Eleven until she rejected him. However, the show itself doesn't confirm this.