Vecna's Plan in Season 5 of 'Stranger Things' Relies on the 12 Kids He Kidnaps From Hawkins

At the start of Season 5 of Stranger Things, Henry, aka Vecna, puts a plan into motion that involves kidnapping 12 kids from Hawkins and using them in his plan to merge the Upside Down with Earth and the other dimension on top of the Upside Down. But why does Vecna need 12 kids, and what significance does that number have for him, if any?

In the end, obviously, it doesn't work out for him. Part of that is because Holly rebels against him, but also because Eleven, Kali, and Max enter his memories to save them. Without the kids, Vecna's plan is ruined, though if he had survived the end of the series, he could have tried again with another set of children.

Vecna never explains in Stranger Things why he needs 12 kids exactly, or why he can't follow through with his plans with one or two less. There is the theme of a clock and its 12 numbers that are important to Henry. The clock's significance is that it was at the Creel house, and in Season 4, it's a reminder for Vecna's victims of his arrival. The 12 kids could be tied to the 12 markers on a clock.

Or, Vecna might need 12 kids because there were 12 kids involved in the experiments at Hawkins Lab. When he was known as 001, and Eleven was, well, 11, there were other kids with their own numbers to signify who they were in the experiments that were done using Henry/Vecna's blood. By taking 12 kids, Vecna is using them like the scientists did, only in his case, he is using them to harness his psychic energy.

The point in Vecna taking the kids at all is to use them to move his plane, the Abyss, through the Upside Down and into Hawkins to merge the worlds together. He never says why he needs 12 kids exactly, but harnessing psychic energy through all 12 kids, or vessels, helps him have more power to do what he needs to do. Well, until Eleven and the rest of the gang stop him, anyway.

In the last season of Stranger Things, the kids that Vecna takes are hooked up to the Mindflayer, much like Will was in Season 1 when he was taken. However, he gets away, though that was likely Vecna's plan for him all along, as he used Will to spy on people and to psychically dig tunnels that would help Vecna in his long-term plan.

He tells Will at one point that he chose him because he was a "weak" child. He chooses 12 children for his overall plan because they are also seen as weak and pliable, but the actual significance of choosing 12 kids exactly before he is ready for his plan is not outright explained.