From the moment that he is born, 001 is a strange and odd child, and he seems to have powers from the very beginning of his life. When he begins living at the Hawkins Lab and Dr. Martin Brenner (Matthew Modine) experiments on him, it's clear that he is different from the other children.
Brenner's children were granted powers by treating their mothers with psychedelic drugs during pregnancy. Henry Creel appears to be different, however; there's no evidence his mother ever experimented with LSD. Rather, his powers seem to be natural, developing around puberty.
For whatever reason, he identified Eleven as the likeliest target for his manipulations and got her to remove a device Brenner had implanted in his neck. The device (called a "soteria," which we explained in our analysis here) had prevented Henry from using his powers or escaping the lab.
The son of Victor Creel, Henry figured out he had psychic and telekinetic abilities when he and his family first moved to Hawkins. He'd initially used his powers to scare his family before he became Dr. Brenner's first subject, a.k.a One.
Remember also that we have evidence that powers can be inherited -- El inherited her powers from Terri Ives, for example. So it stands to reason that Henry inherited his powers from one of his parents.
In fact, it is possible that Henry Creel's psychokinetic powers are naturally occurring. While it may be a side effect of her involvement in Project MKUltra, Eleven's mother, Terry Ives (Aimee Mullins), exhibited limited psychokinetic abilities of her own.
While the source of Vecna's powers is never explained, there are some Stranger Things hints leading to the theory that Hawkins had a big part in awakening them. Vecna is revealed in season 4 to be the base cause behind all of Hawkins' unfortunate happenings for the past three years.
He gets punished with electrocution after telling Eleven that Dr. Brenner lied to her about her mother dying during childbirth. He's smart enough to use an ostensibly harmless game of chess with Eleven to inform her Dr.
That being said, Eight's superpower was performing illusions, so it's entirely plausible she made herself invisible and escaped before or during 001's frenzy.
Identifying with Eleven, One wanted to kill everyone else and reshape the world with their combined powers. Eleven turned him down. They do battle — which we'll get to — and Eleven banishes One to the Upside Down. He transforms into the Vecna.
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).
The boy, who was named and tattooed “001,” was the first of Brenner's experiments. When Eleven defeated him, he was cast into the Upside Down and his body was mutilated by the warped lighting as he fell.
Then, as he was falling through the Upside Down, One became the creature Vecna after lightning struck him in such a way that it changed his skin and made him into the monster he is now. Stranger Things Season 4 Part 1 is out now on Netflix, and Part 2 will be released on Friday, July 1.
The Duffer Brothers had Vecna planned from the start, which is how they were able to tie his character into earlier seasons. Stranger Things revealed Vecna was also behind the Mind Flayer that appeared in season 2.
It seems that the reason why Vecna wasn't killing for the seven years after the Hawkins Lab massacre was because he was waiting to become more powerful as the Mind Flayer and Demogorgons took more victims, as he was likely weakened after being thrown into the dimension.
One manipulated Eleven into plotting her own escape, which also involved getting her to remove the device in his neck. (Henry, however, did not tell Eleven the truth when he said Brenner wanted her dead.
Kali Prasad is a former Hawkins Lab child, known as 008/Eight, who managed to somehow escape before the massacre in 1979.
Henry Creel/Vecna/Number One had a fascination with spiders since being a young boy. He forms a sort of kinship with them, describing them as ''misunderstood'' and ''solitary creatures,'' to which he feels he can relate.
In a flashback, he has a conversation with Eleven and briefly mentions Kali isn't present at the lab at that time. This means she escaped from Hawkins Lab before the massacre, hence, why she's still alive.
There are still a few details we don't know, but it's clear that Brenner secretly kept Henry around as an orderly and the chip in his neck was some kind of power suppressant. Without it, Henry is able to unleash his powers on those in the lab, slaughtering nearly everyone, including the children.
In episode 7, Vecna is revealed to be Henry Creel (played as a youngster by Raphael Luce), the son of Victor Creel (Robert Englund) and his wife Virginia (Tyner Rushing) shown in the 1950s flashbacks.
In a fit of rage, Henry used his restored powers to brutally murder the other test subjects and workers, and attempted to do the same to Eleven. However, Eleven stood her ground and ultimately overpowered him, sending him through a gate to the Upside Down; there, he gradually transformed into the being known as Vecna.
Vecna's 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. The design of Vecna's hand is also a nod to Freddy Krueger, the Nightmare on Elm Street villain who had a huge influence on this season in general.
He was initially trained by his mother, Mazzel, in the art of magic, before she was executed by the government of Fleeth for practicing witchcraft. Vowing revenge, Vecna eventually assumed a mastery of the dark arts achieved by no mortal before or since.
Finally, the Ur-Flan had a strong association with necromancy magic, many of whom aspired to and eventually did become undead, Vecna included. Vecna was trained in the art of sorcery by his mother Mazzel, who was eventually executed by the government of Fleeth for practicing witchcraft.