After five seasons across nearly 10 years, “Stranger Things” reached its grand finale in 2025 as the monster-hunting, D&D-loving party took on the show’s big bad, Vecna, for one last time. Making Vecna a credible, terrifying threat took a lot of teamwork, with actor Jamie Campbell Bower, prosthetics designer Barrie Gower and casting director Carmen Cuba putting their heads together on how to create a finale-worthy villain. “It really was just su…