Linith (also romanized as Rinis, Ryrith, or Ririsu) is an artificial cat familiar created by Precia Testarossa during her artificial mage research. Originally the Testarossa family's household pet while Alicia was alive, Linith was transformed into a familiar to serve as Fate Testarossa's magic instructor during Fate's childhood. Her primary responsibility involved educating Fate in fundamental magic theory and combat tactics over roughly two years. Within this period, Linith personally designed and constructed Fate's intelligent device, Bardiche, to complement Fate's developing magical abilities. She also guided Fate through the intricate process of creating her own familiar, Arf, providing both technical expertise and emotional support during the summoning ritual. Linith consistently demonstrated compassion towards Fate, offering emotional nurturing that contrasted sharply with Precia's abusive treatment. This mentorship established Linith as Fate's primary positive parental figure throughout her isolated upbringing. Her training methodology emphasized practical application, utilizing simulated combat scenarios to hone Fate's tactical decision-making and spell execution. Following the completion of Fate's training, Linith's physical form dissipated according to Precia's design, abruptly removing Fate's sole source of emotional support. This departure occurred immediately before Fate's deployment to Earth for the Jewel Seed collection, compounding Fate's emotional vulnerability during her initial confrontations with Nanoha. Within the movie continuity, Linith's expanded backstory and interactions with Fate originate from supplemental materials, specifically Nanoha Sound Stage 02, detailing events two years prior to the main narrative. Her inclusion in the film adaptation represents a narrative expansion compared to the original television series, where her character was absent.