Supergirl Faces a Difficult Choice in "Battles Lost and Won" Season Finale Preview

The CW has released a preview for "Battles Lost and Won," next week's finale to Supergirl's third season airing June 18.

The previously-released synopsis provided very little information for the episode, noting only that Supergirl (Melissa Benoist) and team will take on Selena (Anjali Jay) in an epic battle for Earth. Thanks to tonight's episode, "Make it Reign", we know a little bit more about what that epic battle may entail -- and why Earth hangs in the balance.

"Make it Reign" revealed that Selena and her Kryptonian Witches have a very sinister plan for Earth. They plan to use Reign to set off a series of cataclysmic natural disasters that will wipe out human life on Earth. Then, with the planet effectively given a clean slate they plan to terraform the planet into a New Krypton. To do this they have to resurrect Reign and, by the looks of the preview above, the only way to stop the Worldkiller once and for all might be to kill her -- something Supergirl isn't exactly keen on doing.

The possibility that she may have to kill Reign in order to save Earth may be the major moment that Benoist told Entertainment Weekly last month would see Supergirl mature and take ownership of her decisions and place in the world.

"With decisions she makes and how things transpire to wrap it up, she's really taking ownership of herself," Benoist said. "She's maturing, which is what I've always wanted for her since season 1. I wanted to see a natural arc of a girl coming into womanhood, because she was almost naive at the beginning, and just charging ahead not really knowing what she was doing. And now, I think she really does, and she is slowly chiseling out her place, wherever she wants to be."

The preview also hints that the Legion of Superheroes will return in some capacity, something that could lead to what co-showrunner Jessica Queller has described as a heart-wrenching situation for Supergirl and Mon-El (Chris Wood).

"There's a lot more coming," Queller said. "Mon-El is going to be a big part of the show through the finale, and it's a heart-wrenching situation. There's a lot of romance and a lot of drama, and I would definitely tune in to see how that will play out."

Supergirl airs Mondays at 8/7c on The CW. The Season 3 finale, "Battles Lost and Won", airs Monday, June 18.