'Supergirl' Inside "Battles Lost and Won" Clip Released

The CW has released a preview for "Battles Lost and Won", the Season 3 finale for Supergirl.

The episode is set to see Supergirl (Melissa Benoist) and the rest of the team face off with Reign as well as Selena (Anjali Jay) and her Kryptonian witches as they move forward with their dire plans to destroy Earth as we know it and make it into a new Krypton. Part of this process involves catastrophic natural disasters, which is what series co-executive producer Robert Rovner says all of the superheroes will largely be dealing with.

"At the end of the last episode we saw Reign and the three Kryptonian witches begin to terraform the Earth," Rovner said in the video above. "So, in this episode we see our superheroes banding together to save Earth and its inhabitants from the natural disasters."

Those natural disasters are no joke, based on what Winn (Jeremy Jordan) says in the clip. He also notes that there is a "100-percent chance of Reign". As a previous preview for tonight's episode teased, Supergirl may be faced with the difficult choice to kill the Worldkiller in order to save the world, something she was very opposed to. However, co-executive producer Jessica Queller says that dealing with Reign will also be a major issue for Sam (Odette Annable), too.

"Sam has to find a way to regain her strength to help fight this battle against her alter ego Reign, and Sam is going to have to go through a lot of trials and like a real hero's journey in order to get the tools and the power to fight for her friends and her daughter," Queller explained.

And if all of that wasn't enough, audiences will see the return of the Legion of Superheroes as well. Promotional images and previews for the episode reveal that Imra/Saturn Girl (Amy Jackson) and Brainiac 5 (Jesse Rath) both return to lend a hand. It's a return that may shed a little light on how Brainy comes to be a major part of Season 4. It was announced last week that Rath is joining Supergirl as a series regular next season.

"We love the character of Brainiac 5 and can't imagine anyone but Jesse Rath in the role," Rovner and Queller told TV Line. "He brings such fun, heart, and brilliance to Brainy, and we're so excited he's joining the cast as a series regular for season 4. We have a lot of great Brainy stories to tell."

Tonight, also will give some idea as to what's next for Winn. Jeremy Jordan is dropping down to recurring status next year, though there are still many stories to come for the character.

"We love Jeremy, and even though he's [not going to be around full-time], we're not saying goodbye to Winn at all," Rovner and Queller said. "We're already breaking big stories for him right now for the fall, and I think the fans will be excited to see what he has coming up."

Supergirl's third season finale, "Battles Lost and Won", airs tonight on The CW at 8/7c.