Over the course of Supergirl Season 3, Reign's whole world will change. Speaking to Entertainment Weekly, executive producer Andrew Kreisberg revealed that the character will have no idea who or what she is when the season picks up, and this year's story arc will lead her to become the Big Bad.
“When we meet Reign, she’s just a woman... Her name is Samantha and she’s a single mom, and she has no idea that she is Reign," Kreisberg explained. "She has no idea that she was the baby in the pod at the end of last season, so the journey that she takes this season is watching her realize her heritage and see how it manifests.”
"When we were figuring out Reign, one thing we’ve never really seen on any of these shows is we’ve never seen the big bad become the big bad,” he added. However, per his comments above, it looks like that's exactly what we'll get in Season 3.
Odette Annable, who plays Samantha/Reign, teased that her character would have "a heartbreaking story" at this year's Comic-Con International in San Diego. "I have a whole year to discover her and so I think it’s nice that I don’t know much," she said. "In the comics, we don’t really know much about Reign. It’s very sort of a surface-level, and I think that… They’re going to take bits and nods from the original character but also make their own character, and so I feel like the pressure is off a little bit in that way, where I can really dive in create something."
"Her story is going to be different than any other villain that you’ve seen on Supergirl Seasons 1 and 2, mostly because she doesn’t come to Earth to go on a killing spree,” she had teased at the time. “She has a very specific agenda that she is out to do, and you will see that story unfold throughout the season."
Returning to The CW on Monday, October 9th at 8 p.m. ET/PT, Supergirl stars Melissa Benoist as the Girl of Steel, David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen, Chyler Leigh as Alex Danvers and Jeremy Jordan as Winn Schott, with appearances by Calista Flockhart as Cat Grant and Tyler Hoechlin as Superman.