Stranger Things 2: Meet the sequel's mysterious new character, Kali 

Warning: The following post contains spoilers from 

starts off with a boom, literally. Viewers are immediately transported to Pittsburgh, Pennsylvania, where a gang of misfits is being chased by local police. The leader of this group? The powerful Kali (Linnea Berthelsen), who can make people think they’re seeing things and leads the police to believe she blew up an overpass.

Her powers are not the only thing Kali has in common with Eleven: She also has a branded number on her wrist (Eight). The two are “sisters,” which we learn in episode 7 of

. “When we started season 2, we wanted to explore whether Eleven had siblings,” explains Matt Duffer. “That led to the creation of that character and the casting of Linnea.”

marks her biggest role to date. The actress was late to watch the first season but her timing oddly worked out. “I feel like it got popular in Copenhagen maybe a couple months later,” says Berthelsen. “I remember telling my boyfriend in October, ‘Let’s watch

.’ Like literally two days later, I got the [audition].”

Before filming, Berthelsen did her own pop culture research. “I watched all the movies they used for season 1,” she says. “And I went back to read

She jumped headfirst into the dark, troubled character, which included creating Kali’s dramatic hairdo. “We tried a couple things but it was kind of a long creative process with the hair,” says the actress. “And then I said, ‘You can go crazy, I don’t care.\'”

Will we see Kali and her gang again in season 3? “I don’t know yet,” says Matt Duffer. “I don’t feel like there’s closure there. It’s definitely a dangling thread. We’re just figuring it out.”

, stay tuned to EW.com all weekend — and for more on Berthelsen and Kali specifically, pick up next week’s issue of 

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