Fate Testarossa emerges as a central figure during the Jewel Seeds incident. Created as an artificial human clone of Alicia Testarossa by Precia Testarossa through the illegal Project Fate, she received Alicia's implanted memories. Fate endured consistent physical and emotional abuse from Precia, who demanded she collect Jewel Seeds to reach the mythical world Al Hazard and resurrect Alicia. This abusive relationship defined her early life, characterized by unwavering loyalty despite the cruelty. Initially encountering Nanoha Takamachi as an adversary over the Jewel Seeds, Fate presented a cold, determined exterior, often wearing her Barrier Jacket outside combat. Nanoha persistently reached out, sensing her underlying sadness. After a decisive defeat by Nanoha, Precia abandoned Fate, revealing her clone origin and declaring hatred. This shattered Fate emotionally. Supported by her familiar Arf and Intelligent Device Bardiche, and inspired by Nanoha's compassion, Fate allied with the Time-Space Administration Bureau to confront Precia, witnessing her demise during the Garden of Time's collapse. Post-conflict, Fate faced legal proceedings as a material witness but was acquitted due to coercion. Adopted by Lindy Harlaown, she became Fate Testarossa-Harlaown, integrating into civilian life on Earth while maintaining her bond with Nanoha. During the Book of Darkness incident, Bardiche received a cartridge system upgrade, enhancing Fate's combat capabilities and cementing her Fragile Speedster style. She developed mutual respect with Signum of the Wolkenritter and played a pivotal role alongside Nanoha and Hayate Yagami in resolving the crisis. Later, Fate became an Enforcer for the Time-Space Administration Bureau, specializing in investigations involving children. She adopted the fellow clone Erio Mondial and the ostracized summoner Caro Ru Lushe, forming a familial bond. As a captain in Riot Force 6, she led the Lightning Squad with Signum as her lieutenant. Confronting Dr. Jail Scaglietti, the architect of Project Fate, during the JS Incident forced her to acknowledge parallels between her past and his manipulation of children. Fate later became co-guardian of Vivio Takamachi alongside Nanoha, sharing a confirmed romantic relationship. In Special Duty Section 6, she continued investigating major incidents like the Eclipse, balancing duties with parenting. The MOVIE 1st adaptation recontextualizes Precia's backstory as an Ignored Expert whose reactor design caused Alicia's fatal accident, adding professional tragedy to her descent. Fate served as a consultant during the movie's in-universe production, ensuring accuracy. The film streamlines her initial battles with Nanoha, introduces Bardiche's Assault form earlier, and visually amplifies key confrontations, like the multi-angle depiction of her Spark End attack.