In 2017 to 2018, Annable played Samantha Arias/Reign, the primary antagonist in season 3 of Supergirl. Sam Arias is a high-ranking L-Corp executive and friend of Kara Danvers’ (Melissa Benoist). She is also, unwittingly and unwillingly, Reign, a Kryptonian warrior sent to Earth to take it over. Sam doesn’t know about Reign, her split personality, until Reign starts to manifest and cause problems in her life. Reign and Supergirl fight throughout the season, while Sam tries to protect herself and her daughter, Ruby. Eventually, Sam is freed from Reign with the help of Lena Luthor (Katie McGrath), and with Kara’s help, is able to defeat Reign for good.
Reign is depicted as the most fearsome foe Kara had ever faced at that point in the series, as they basically had all the same powers, both being genetically-engineered Kryptonians. Reign can fly, is invulnerable, has super-speed and super-strength, and has the ability to create and spread a deadly plague. But in the end, she proves no match for Supergirl and her friends.