She is portrayed by Laura Benanti who also played Alura Zor-El.
On Krypton, Astra and her sister Alura often argued. When Alura's daughter Kara asked her mother about it, Alura claimed that it was because Astra had no faith in people. However, despite her differences with her sister Astra often tended to her niece Kara, teaching her the name of the stars while Kara sat on her lap. She and Kara also had "spy-beacons", allowing them to communicate via distances. Astra was the one who told Kara that Krypton was dying because its core was unstable. At that point, Astra considered Kara as a daughter.
Eventually, the falling out between the sisters reached their conclusion and Astra was forced to flee the capitol. Now undercover, Astra and her fanatical husband Non blew up a governmental building to show the people of Krypton that they had to change their way of life to save their planet. Unfortunately, Non killed a guard on the way. Because of this Astra was forced into hiding but was drawn back home by Kara's spy beacon. Astra met her niece but Alura arrived and sent Kara away. Alura then confronted her sister with her acts, begging her to return home. Alura offered to pledge her case in front of the High Council and promised that while Non would be imprisoned for life Astra would receive a mild punishment. Astra however claimed that she could hardly care about prison while their planet was dying and that she didn't care how many laws she broke if it would mean Krypton's survival. Unable to let Astra continue her crusade, Alura had her sister arrested by two guards. Astra was imprisoned at Fort Razz in the Phantom Zone, however before she was teleported to the Phantom Zone, she had one last conversation with her sister. Alura told her that while she believed that Krypton faced annihilation Astra's ways were wrong. She promised Astra that she would fight for her cause but not through fear and terror but with compassion and reason. After telling her sister that she loved her, Alura teleported Astra to Fort Razz. Astra's banishment ensured her survival, as she was on Fort Razz when Kryton and everyone on it was destroyed.
After Vartox has failed to kill Supergirl, the Commander contacts his superior Astra. He reveals to her that while Vartox failed to kill Supergirl he was able to find out that Supergirl is Kara Zor-El, Alura's niece. Astra states that while her right to rule Krypton was taken from her, she will not lose earth the same way. She orders the Commander to find Kara and kill her, not letting that fact that she's her niece get in the way of her evil agenda.
In the second episode, "Stronger Together," Astra sends a Hellgrammite, a kryptonian criminal after Kara, and later captures Kara's sister, Alex Danvers, to lure Kara to her. Her trap works, as Astra attacked Kara after she arrived to save Alex. After Astra reveals that Alura had her imprisoned, she fights Kara, while attempting to convince Kara to join her in her quest. She is later stabbed in her right arm with a kryptonite knife by Hank Henshaw and retreats afterwards.
Meeting Kara again
Astra resurfaces eventually, attacking Supergirl with two of her henchmen. After the two men grabbed Kara, Astra revealed herself to her, holding Henshaw's kryptonite knife to her throat. The kryptonite immediately weakens Kara, who is suprised that Astra isn't affected. Astra reveals to her that as with every dangerous substance one must find to shield onesself, showing Kara that she built a suit that protects her from the mineral. She then claims that she hasn't come to fight Kara but to allow her niece to rejoin her family. Kara however refuses, stating that she hates Astra, and flies off.
Some time later, Astra is chided by her husband Non for failing to kill Kara. Astra reminds him that she is his general and that he owes her his allegiance. Non demands that Astra lets him go to kill Kara, as Astra herself clearly isn't able to do so. Astra forbids it and further claims that she will see their plan through as she won't allow another planet to die when she could save it, but Non claims that should Astra die he would hunt down and kill Kara.
Astra later reveals herself to National City, hovering over the city and demanding Kara. Eventually, the media picks up the story and Kara flies up to meet her aunt. Astra reveals to Kara that she came without knife and guards. She claims that Kara can hardly say that their fight wouldn't be fair but Kara responds that they are done with fair. A battle over National City ensues, with the two Kryptonians smashing into a skyscraper. One of the fragments threatens to smash a group of civillians so Kara grabs it and hurls it into her aunt. The fight ends with Astra smashing Kara into the ground at a park in National City. Standing over her niece, Astra claims that Kara once again reminds her of Alura. Kara spits at Astra that her mother was a better person than Astra would ever be, but Astra replies that Alura was a murderer. Kara calls her a liar but Astra reveals that Alura had to make someone else responsible for her own cruelty and weakness. Kara states that Alura's only weakness was letting Astra live and, fueled by her rage, manages to get up and smash Astra into the floor. She proceeds to beat her aunt but hesitates to deliver the finishing blow, unable to kill her last living relative. Instead, she delivers Astra to the D.E.O. who lock up Astra after binding her with kryptonite handcuffs. Alex tells Kara that she will call her immediately when Astra wakes up, but Kara tells her not to, prefering to let her aunt rot in her cell.
However, after waking up Astra claims that she will only talk to Kara. Kara returns to the D.E.O. and faces Astra, who reveals that she still has the "spy beacon". Astra reveals that she took it with her when she fled to remind her why she was betraying her family and the High Council, to assure that what she did was worth it should it allow Kara to survive.When Kara confronts her with the lives Astra and Non took when they blew up the buildings, Astra claims that they did what they had to and that Alura is the one with blood on her hands. Kara doesn't believe her, instead claiming that Astra lost her mind while imprisoned in the Phantom Zone. Astra reveals the circumstances of her imprisonment to Kara and states that she holds Alura responsible for the destruction of Krypton, as Astra's imprisonment stopped her from continuing her mission. She also tells Kara that, like Krypton, earth stands on the verge of ecological destruction. She reveals that she can stop it but that the humans won't like her methods. She begs Kara to help her but Kara storms out of the room. While the doors close, Astra cries that she loves Kara but her niece doesn't listen.While rewatching footage of Astra's fight against Kara, Alex and Henshaw find it suspicious that Astra, who beat Supergirl twice, lost so easily. They also find it unnerving that not one of Astra's soldiers have come looking for her. They realise that Astra wanted to be caught and head to her cell to make her talk. Astra recognizes Alex as the one who defeated the Hellgrammite but tells her that she has come too late. The same moment, Astra's forces led by Non invade Lord Technologies. Although Non's men are defeated by the D.E.O., Non escapes with Henshaw as a captive. Kara returns to Astra's cave to find out where Non is located. However, Astra does not give her any information anf further states that Non only didn't kill her because Astra forbade it. Non later contacts the D.E.O. and offers to trade Henshaw for Astra. After General Lane gains control over the D.E.O. he visits Astra in her prison. As he views Astra as a threat to humanity, he threatens to inject her with kryptonite should she not reveal the location of Non's base to her. Supergirl and Alex enter the room, trying to stop Lane but as Kara is also weakened by the kryptonite in the room she is not able to save Astra. While Alex drags Kara out of the room, Lane injects Astra with the first dose of kryptonium. Astra eventually yields up the location of Non's base and the D.E.O. heads to save their former director. However, they find that Non set a trap for them and placed a bomb inside one of the containers at the "base". Supergirl is able to shield off Alex but the rest of the present D.E.O. soldiers succumb to the blast.
Kara later returns to Astra, ready to hear what her aunt has to say. Although Astra claims the aunt Kara knew died on Krypton, Kara replies that she has faith that there is good left in her. After revealing that Alura never lost faith in her, Astra tells Kara that the only way to save Henshaw would be the exchange. Despite General Lane's objections, Kara and Alex later leave the D.E.O. with Astra to make the exchange. Once Non arrives with Henshaw, Alex removes Astra's kryptonite chains and Astra walks towards Non while Henshaw returns to his men. However, once Astra is safe her soldiers arrive and surround the D.E.O. and Supergirl. Non tells his men to prepare to attack but Astra tells the men to stand down. Reluctantly, Non accepts and tells the soliders to withdraw. He then flies after them, leaving Astra alone. Before Astra follows her men, she warns the D.E.O. not to see this as a truce. She then lifts off, leaving the D.E.O. alone.
During the solar storm, which is crucial to Astra's plans, Astra is informed by Non that Non left a Black Mercy, a parasitic plant which puts its victims into a deep hallucinogetic sleep, at Kara's apartment. Astra is furious but Non claims that he did obey her orders, which were that Kara would remain unharmed, and that Kara is at peace now which is more than she deserves. To save Kara, Astra visits Alex at her apartment and reveals to her what the Black Parasite is. She also claims that Kara must reject the hallucination herself in order to wake up but that there is a possibility to enter the virtual reality and help her wake up.
Back at her base, Astra and Non brief their men about their plans. After, Non asks Astra where she was. He asks her whether her heart is in their operation and Astra states that they will save the planet by bringing humanity to its knees. Recognizing the honesty in her voice, Non apologizes to Astra for doubting her.
After Kara is saved from the Black Mercy, the D.E.O. finds out that the day Non attacked Lord Tech he did not steal anything but left something behind, a computer virus that gained him access to Lord Tech servers and allowed him to override the civillian network. They realise that Non and his men must be targeting the six other server farms around the city and the D.E.O. sets out to protect the server farms. Kara goes with them, bent on revenge for what Non did to her. At one of the server farms, Alex meets Astra who is about to sabotage it. Although she swiftly overpowers Alex, she is then attacked by J'onn J'onzz. She manages to fend off J'onzz long enough to use her virus on the server, then continues their fight. She overpowers J'onzz and is about to kill him when Alex approaches her from behind and drives a kryptonite blade through Astra's chest.
Kara arrives in time to share last words with her dying aunt, who reveals to Kara that she is glad that Kara survived the Black Mercy. With her dying breath, Astra begs Kara to stay awaxy from Non as he cannot be stopped and would kill her should she get in his way. Astra then dies, and Kara, J'onzz and Alex are forced to flee when they see some of Astra's soldiers approaching. After Astra's death, Non takes control over her soldiers.
- Astra is not from any of the comics. She was solely created for the Supergirl TV series.
- Though Alura and Astra are identical, Astra has a grey streak in her hair.