Before the civil war that divided Patria, Beatrice was a professional singer who brought joy to the audiences in the northern port city of Newfort. Her voice had a special, almost supernatural quality that could lift the spirits of those who heard it. However, as the war gripped the nation and fear replaced hope in the hearts of the people, Beatrice found that her songs could no longer provide comfort. Her audiences dwindled, and she was left feeling hopeless and lost, horrified by the suffering around her and her own inability to ease it.

Her life changed when Captain Hank Henriette of the Incarnate program recognized the unique power in her voice. He offered her a way to end the war and the pain it caused by becoming an Incarnate, a human granted the god-like abilities of a mythical beast. Beatrice accepted this offer, transforming into a creature known as a Siren. In this form, her legs fused into a large, muscular fish tail, and her arms became grand, white, bird-like wings. Although she could not truly fly, these wings could vibrate to create her deadly song, which directly attacked the nervous system of its victims, first dulling their senses before inducing a fatal, comatose state. Her body, however, remained quite frail, making her vulnerable to direct attack. On the battlefield, she was paired with Danny, an Incarnate with a massive, rhinoceros-like form who would carry her and serve as her shield. As she killed countless enemy soldiers with her voice, she became known to her comrades as Siren.

Following the war, the Northern Union of Patria ordered the execution of all Incarnates, viewing them as threats to humanity. Beatrice was forced to hide, living like a mermaid in the waters around the dockyard of Newfort to avoid capture and the prejudice of the people she had once fought to protect. She initially tried to find happiness in this isolated existence, but any peace was shattered when she overheard that the actions of a former comrade, Cain Madhouse, were about to spark a second civil war. Having witnessed the agony of the first war firsthand, Beatrice was driven to despair. She resolved to "save" the people of her hometown from enduring another such tragedy by putting them into a permanent sleep with her song.

When the Incarnate extermination unit, Coup de Grace, arrives in Port Gulf, Beatrice is found by Claude Withers, the unit's captain, and a young woman named Schaal Bancroft. Schaal, who is searching for Hank Henriette, refuses to listen to Beatrice's song of despair, offering instead a connection that the lonely Siren has desperately missed. This encounter forces a final, tragic confrontation. Beatrice reveals her past, her love for singing, and her profound disappointment that her post-war form has left her unable to share her music. Ultimately, after being fatally wounded, she returns to the bar where she once performed. There, she asks Schaal to listen one last time. With her final song, Beatrice dies peacefully in Schaal's arms, having been seen not as the monster Siren, but as the singer Beatrice, whom her friends called Trice.