SPOILER WARNING: This article contains major spoilers for "Fort Rozz," the latest episode of Supergirl.
Longtime Supergirl villain Livewire just sacrificed her life to save the Girl of Steel. In "Fort Rozz," the latest episode, Leslie Willis accompanied Supergirl to Fort Rozz, where she leapt into Reign's line of fire to prevent her from killing Kara.
In order to get answers about Reign's mission, Supergirl recruited Livewire, Psi and Saturn Girl and headed to Fort Rozz to find a priestess that had been incarcerated there. However, after Supergirl had launched it into space in Season 1, it got caught in the orbit of a blue sun. This blue sun not only negated her powers, but also emitted a special kind of radiation that is deadly to any creature with a Y chromosome. As such, Supergirl needed some girl power to back her up when she went looking for the priestess.
Livewire agreed to accompany her only begrudgingly. The deadly villain had gone underground, working as a waitress in order to avoid Reign's wrath. Though she turned Supergirl down at first, she ultimately agreed to help out so that she could prevent Reign from killing more of her friends.
After a solar flare sent Fort Rozz and the Legion's ship careening into the sun, the team split up so that Supergirl and Livewire could track the priestess down while Saturn Girl and Psi fixed the damage the flare had caused. Supergirl eventually found the priestess, who let slip that Reign isn't the only Worldkiller. However, before she could learn more, Reign -- who was able to maintain her Kryptonian powers -- showed up and killed the priestess.
Without her powers, Supergirl was helpless -- and that's where Livewire stepped in. The two went toe-to-toe, with Reign eventually overcoming Livewire. Before Reign could unleash her laser vision, Supergirl begged her to reconsider; after all, Reign had come to destroy Supergirl, not Livewire. As Reign geared up to do just that, Livewire leapt in front of Supergirl to save her "friend" from certain death. Livewire took the full brunt of Reign's laser vision and died moments later. Because of Livewire's sacrifice, Supergirl, Saturn Girl and Psi were able to return safely home.
Livewire debuted in a Season 1 episode that was named for her. A former shock jockey, she was imbued with the power to control electricity after a lightning strike. She blamed Supergirl for her transformation and went up against the Girl of Steel in an additional two episodes, including the first Supergirl/The Flash crossover "Worlds Finest."
Airing Mondays at 8 p.m. ET/PT on The CW, 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.