The third season of The CW's Supergirl has seen the Girl of Steel deal with her most formidable foe yet -- the Worldkiller, Reign, and before the show went on hiatus until April it was revealed that Reign isn't alone. There are other Worldkillers in National City, just waiting to team up with Reign.
While one of those other Worldkillers was revealed to be Julia Freeman/Purity (Krys Marshall), Kara Danvers/Supergirl (Melissa Benoist) saw yet another Worldkiller in her vision. That third Worldkiller's face was obscured, and her identity has not yet been explored on the show, but some fans think they may have already solved that mystery: the third Worldkiller could very well be Kara herself.
According to the theory, Kara being the third Worldkiller would stem from a variation of the Worldkiller story in comics. In comics, Kara's father is involved in the creation of the Worldkillers, and, as the theory for Supergirl goes, on the show it would be Kara's mother Alura (Erica Durance) who was secretly involved in their creation. The first piece of evidence that Kara has a connection to the Worldkillers through her mother came at the beginning of the season. Both Kara and Sam/Reign (Odette Annable) had a nearly identical dream featuring Alura. Alura is seen walking in a field in both women's dreams, though in Sam's Alura turns into a demon-like figure. That similar dream could indicate a deeper connection between Sam and Kara than both of them simply being from Krypton. It could mean that Kara herself is a Worldkiller.
But how? It's possible that in the past, Alura was part of the Kryptonian cult responsible for the creation of the Worldkillers, but at some point -- perhaps when the cult involved Alura's own child -- Alura had a change of heart. The rest of the cult was imprisoned on Fort Rozz, but not before Reign and Purity were sent to Earth. Alura then raised Kara herself, with Kara only being sent to Earth when Krypton died. As Kara had a different childhood than Reign and Purity, Kara has a very different mindset and a different sense of Kryptonian duty. This could be why Kara hasn't exhibited Worldkiller abilities at this point. However, even if didn't have the same early years as Reign and Purity, the Worldkiller programming is still inside of Kara. If Kara discovered her secret Worldkiller heritage, she might be able to tap into it and use her newfound powers to defeat Reign.
It's also possible that those buried Worldkiller tendencies will surface and lead Kara to side with Reign, which might also explain the Legion's secret mission. Perhaps they are there to turn Kara away from being a Worldkiller, thus saving the Earth from an impending catastrophic event in its future. Having Kara secretly be a Worldkiller would be an interesting and unexpected twist, one that would fit into this season's exploration of identity for Kara. In an interview ahead of the season premiere last fall, Benoist explained that Kara would question who she wants to be this season.
"It's a couple of months past where we left off. When we pick up in season three, Kara has very much dedicated herself to Supergirl, and I don't think she really wants to address what happened for Kara Danvers personally, because that was such a massive heartbreak for her," Benoist said. "So, the balance is a little off-kilter right now, and this season I think we're really going to explore her identity. She's really questioning whether she's human or an alien and which she wants to be."
Supergirl airs on Monday nights at 8 p.m. ET/PT on The CW. New episodes resume on April 16th.