Lucina

History
The daughter of Chrom and Robin and gifted with the mark of Naga, known as the Brand of the Exalt, on her left eye, like in the present timeline, future Lucina was born to Chrom and Robin after the Ylisse-Plegia War. She had a special bond with her parents, especially Chrom who taught her swordplay.

After Chrom's death at the hands of Grima, Lucina inherited the Falchion and attempted to fight Grima. She never learned who killed her father, however, her only clue was that her father's murderer was someone close to him. At some point, her mother was also killed in battle. With the world on the brink of destruction, Lucina was down to only her closest allies, the other children of the Shepherds and her brother Morgan.

Ylisse-Plegia War
While traveling into the past, anomalies in the flow of time due to the presence of Grima and his Risen army following the children caused her to be separated from her friends, while she herself arrived shortly after Chrom had just recruited his most trusted ally, Robin. Upon arrival from the future, Lucina, under the guise of "Marth", instantly comes to Chrom and Lissa's aid when a Risen nearly kills Lissa. However, before Chrom can thank her, she temporarily leaves, leaving Chrom, Lissa, Frederick, and Robin to fight off the remaining Risen that appeared from the portal. After the battle, she introduces herself as Marth and then promptly leaves, warning them of greater dangers to come. Later, during a tournament at Arena Ferox, Lucina defeats Basilio's original champion, Lon'qu, thus becoming his new champion for the tournament. Chrom defeats her in the tournament and once again, she leaves.

After the Shepherds rescue Maribelle, Plegia plans an assassination on Emmeryn. Lucina appears before the attempt and tells Chrom that she will protect him from an Assassin hiding in a nearby bush. The Assassin pops out and is quickly killed by her. However, a second Assassin appears, and manages to cut her mask off, causing her hair to come loose, and exposing the fact that her gender is female, but Chrom kills the second Assassin. She assists Chrom in protecting Emmeryn from the assassins, led by Validar. During the attempt, Panne appears and Lucina tells Chrom that she is not hostile towards them. After Validar's death, Emmeryn thanks her and she leaves, believing that the future has been altered. However, she watches Emmeryn's death and is horrified that her future is back on track.

Two years after Gangrel's defeat at the hands of Chrom, the present timeline's Lucina is born to Chrom and Robin.

Conquest of Valm
After talking to the new king of Plegia, Validar, at Carrion Isle, Chrom and Robin prepare to depart the next day. That night a group of Risen ambushes Chrom's army. After clearing nearly all of the Risen, a Risen Assassin suddenly warps behind him, but Lucina steps in and protects Chrom, though in the process, she calls Chrom "father", blowing her cover as "Marth" even more. Chrom is still curious as to who she is and Lucina can no longer bear to hide her secret from him. Lucina tells Chrom to look into her left eye. As he gazes closely into her eye, he sees the Brand of the Exalt, the exact same one that his infant daughter has back at Ylisstol. Lucina begins to tear up, but Chrom warmly wipes away her tears. Lucina finally embraces her long lost father, weeping in his arms.

Robin soon arrives and becomes upset and shocked upon seeing Lucina, believing that Chrom had a secret relationship. Lucina clears all misunderstandings by showing her the Brand in her eye. After reassuring them that the present Lucina is still in the castle, Robin happily accepts her and they share a tender embrace. Collecting herself from the reunion, Lucina reveals to Chrom, Robin, and Lissa of the apocalyptic future she came from where the Shepherds were all killed, leaving behind only their children. With the resolve to change the future and to protect her parents, Lucina joins the army. And while on the ship to Valm, Lucina decides to ditch the "Marth" name, preferring to fight as herself now.

After capturing Fort Steiger from the Valmese, Chrom receives alarming news that the forces up to the north were crushed by Walhart's forces, and the forces to the south were destroyed by Yen'fay's forces. When Khan Basilio volunteers to stall Walhart's army while Chrom and Robin's troops attack Yen'fay, Lucina steps in to try and stop him since, in her timeline, Basilio perished when he went. Nevertheless, Basilio's resolve is stronger than Lucina's warning, though Flavia decides to go to increase his chances of survival. Soon after, word arrives that despite the different events, Basilio was "slain" regardless. Remembering his sacrifice, Chrom's army finally take down Walhart's forces, once and for all.

Fate of the World
After preventing Walhart's conquest, Validar sends a message to Chrom so he can give the final gemstone for the Fire Emblem. On the way to the castle, Lucina sees what appears to be Grima's remains, telling Chrom that Grima must not be resurrected in this timeline. Upon reaching Plegia's castle, Validar betrays the group and tries to seize the Fire Emblem from Chrom, forcing them to flee. Chrom, Robin, and Lucina nearly make it out of the castle, but Validar warps in and weakens Chrom. Validar orders Robin to seize the Fire Emblem and Robin does against her will. After seeing the event unfold, Lucina realizes that Robin was the one who murdered Chrom, despite that act was against her will.

After escaping the castle, Lucina thinks about killing Robin to prevent this, But in the end cannot bring herself to kill her own mother.

Later at The Dragon's Table, Lucina witnesses Robin killing Chrom again and cries out in horror. Chrom soon gets back up on his feet however, surprising both Lucina and Validar. Robin, having foreseen the event in a Premonition. Basilio is also revealed to have survived his encounter with Walhart, having taken Lucina's advice and feigned death. They then put Validar out of his misery and all seems well. However, a mysterious black figure warps in and takes on the appearance of Robin, revealing herself to be Grima. Grima reveals that he is indeed the one who possessed Robin in the alternate future and followed Lucina into the past. He is able to revive the dragon body of the present Grima, causing Lucina to look in horror as she remembered what had happened in her future. Nonetheless, all is not lost, as Robin managed to steal the Fire Emblem from Validar before it was dropped into the Dragon's Table. Now with the power to take down Grima, Lucina aids Chrom and Robin for the final battle with Grima.

After defeating the Fell Dragon, Lucina goes to Ylisstol and whispers to her infant self that she will live a better life than she did and promptly leaves, Along with her lover Severa they leave without a trace. Lucina later has a daughter with Severa.

Support

 * See main article Lucina/Support