WARNING: The following contains major spoilers for "Rebirth," the Season 6 premiere of Supergirl.
Following her costume reveal in the Supergirl Season 5 finale, Alex Danvers has chosen her very own codename as well. After a conversation with J'onn J'onzz, she decided to take the name Sentinel, after a Martian warrior he had known a long time ago.
As "Rebirth" wound down, Team Supergirl dealt with the price they paid to stop Lex Luthor. With Supergirl trapped in the Phantom Zone, they considered their next steps, as well as what her absence means for them as individuals. For Alex, that meant life -- and, more specifically, a journey to becoming a superhero -- without her sister.
"I need my sister," she insisted to J'onn. "The people out there -- Nia covered for her at CatCo, but everyone else? They need to know that she's still around, that she's protecting people!"
"You are not your sister, but you're every part a hero that she is," J'onn reassured her. "I've seen that every day I've spent with you, and I saw it today when you summoned the strength and belief in yourself to take down Lex Luthor. In fact, you remind me of a colleague I once had on Mars, called N'orr Cott. We were a team. Every time I'd put criminals away, she would always stand guard, in case of a surprise escape or an ambush. She had patience, courage and commitment, just like you. We called her Sentinel."
With that, he turned towards the wall where all the heroes' symbols hung. "I want to show you something," he said, presenting her with a new placard to add to it. "This was her symbol. I think it should be yours."
Alex pursed her lips. "Sentinel," she mused, offering him a sad smile. "I like that." So, with her approval, he added it to the wall, next to Supergirl, Batwoman, the Flash, Martian Manhunter, Dreamer and Brainiac-5.
Last season, Alex finally took up a superhero persona after her girlfriend Kelly Olson suggested it. However, this seems like a natural progression for the character. Up until "Crisis on Infinite Earths," Alex had worked for the Department of Extranormal Operations (DEO). Then, when Lex rewrote reality to become head of the DEO, Alex quit. After that, she felt adrift.
This -- coupled with her father's death -- eventually drove Alex into Obsidian's virtual reality, where she masqueraded as Supergirl. Although it eventually went terribly wrong, the experience helped her develop a taste for helping others as a vigilante as opposed to a government agent. As such, it isn't a surprise to see Alex adopting her own vigilante persona.
Supergirl stars Melissa Benoist as Kara Danvers, David Harewood as Martian Manhunter, Chyler Leigh as Alex Danvers, Nicole Maines as Dreamer and Jesse Rath as Brainiac-5. New episodes air Tuesdays at 9 p.m. ET/PT on The CW.