'Supergirl' Season Finale Recap With Spoilers: "Battles Lost and Won"

"Battles Lost and Won" starts with National City suffering an earthquake. Team Supergirl is trying to evacuate as much of the city from harm as they can.

Realizing that Reign could cause the end of the world, J'onn and M'yrnn continue their ritual of transferring memories. M'yrnn shows J'onn the origin of the Sacred Scrolls.

Imra and Brainiac-5 return to National City to help out. J'onn, dressed up as Guardians, runs into a burning CatCo building to rescue an employee's child. He reveals his identity to the CatCo employee.

M'yrnn and J'onn finish their ritual and M'yrnn apologizes for not being able to transfer all of his memories under their current situation. J'onn and M'yrnn say their goodbyes and M'yrnn passes away.

Team Supergirl momentarily stops Reign from causing any additional harm.

J'onn returns to the DEO and reveals that M'yrnns sacrifice is what trapped Reign under the crust of the Earth.

Sam wakes up in the dark mirror dimension. She's immediately approached by her mother and starts to freak out.

At the Fortress of Sanctuary, Coville wakes up — he apparently survived Reign's attack.

Mon-El speaks with Imra at the DEO and thanks her for coming back to help out. The two embrace. Brainiac-5 finds Mon-El sitting in a room by himself at the DEO. Winn soons joins the two and Brainy reveals that his distant cousin is taken over all technologies in the future.

Brainy explains that the Legion needs Winn's help in the future, revealing that Winn's technology has saved many people in the future.

The Daughters of the Night continue their ritual at the Fortress of Sanctuary and they're able to pull Reign back out from the center of the Earth. Wanting to escape, Coville can be seen crawling towards the Daughter's Kryptonian spaceship.

Lena and Alex are looking over Sam's lifeless body as her consciousness is still in another dimension. The two begin talking about Alex's wants of starting a family.

Elsewhere, Winn is talking to James about Brainy's offer of joining the Legion. Winn admits he'd be afraid to leave James, Kara, and the rest of Team Supergirl back in National City. James tries to put Winn at ease by revealing he shared his true identity to a National City resident earlier in the day.

An alert starts going off at the DEO and the group finds out that Selena's ship is broadcasting a distress signal. It gives them the location of Selena's ship.

In the dark dimension, Sam's mother begins singing her a lullaby to calm her down. Sam realizes the apparition is actually her mother and not something her mind is making up. Sam instantly calms down and her body wakes up at the DEO and she begins flying - Sam has gained Reign's powers.

Kara, J'onn, and the Legion arrive at the Fortress of Sanctuary to confront Reign and the Daughter of the Night. The two sides instantly start fighting. The group easily takes care of the Kryptonian elders but Reign suddenly gains the upperhand. She's about to kill Kara when Sam runs in and stabs Reign in the back.

Sam and Reign fight and Sam eventually tosses Reign in the pit in the Fortress. Before going down the pit, Reign uses her lazer vision to apparently kill Sam, Mon-El, and Alura.

Upset at what she's caused by refusing to kill Reign, she takes Mon-El's ring and convinces Winn to use Legion tech to send her back in time. Going back in time, Kara's able to stop Sam from killing Reign. Instead, Kara transports into the dark dimension with Sam and Reign and Sam poisons Reign with the deadly water her mother warned her about.

Reign dies and Kara and Sam escape back into the proper timeline. Kara's brooding over National City and she's approach by Mon-El. He congratulates her on stopping Reign and Kara talks to him about how she thinks Earth is home over a place like Argo City.

Mon-El starts tearing up and reveals to Kara that he needs to go back into the future with the Legion.

At the DEO, Sam and Ruby talk to Lena and Alex.

Winn looks down at the drawing Brainiac-5 gave him and realizes he has to join the Legion. He tells James about that and James agrees with Winn's decision.

Alex approaches J'onn about her role with the DEO. She expresses frustration that her job hasn't allowed her time to start a family. She gives J'onn notice so she can leave the DEO and start a family.

J'onn stops meditating and tells her that he wants to promote her. J'onn reveals that M'yrnn has showed him to return to his people on Mars. He reveals he's stepping down and wants Alex to take his place as the Director of the DEO. Alex takes the position and the two hug.

Alura tells her daughter goodbye. She informs Kara that the Daughters of the Night will be subject to a fair and just trial.

Winn starts saying his goodbyes to his colleagues at the DEO. Winn joins the Legion and it's revealed Brainiac-5 has remained on Earth to take Winn's place at the DEO.

James and Lena are hanging out when James' phone rings. It's a reporter asking for a comment on a story about his identity as the Guardians. James reveals to the reporter that he is, in fact, Guardian and it turns into breaking news.

Later that night, Alex and Kara are watching the news talking about their lives. Kara congrats her sister on becoming Director of the DEO.

In her lab, Lena fields a call. It's revealed she's working on a secret project with the black rock from Argo City.