Fiona was born in the Fortress Cliff Zone, an isolated island locale of vast, emerald-green central plains and mountainous coastlines where towering cliffs plunge straight into the churning sea. The zone's namesake is the numerous stone fortresses (some dating back centuries) perched precariously atop these cliffs like silent sentinels. These fortresses have served as defensive strongholds against pirates and storms as well as communal strongholds for extended family clans. One such fortress was the home of Fiona's family, a long line of foxes known for their cunning, resilience, and tight-knit loyalty. Their lives equally revolved around the land and sea: they fished from small boats launched from hidden coves at the cliff bases, gathered seaweed and shellfish, and maintained the fortress's defenses and communal spaces.

As a young kit, Fiona was adventurous and quick-witted, often scrambling along the narrow cliff paths, exploring tide pools, or listening to elders' tales of ancient fox tricksters who outsmarted sea monsters or rival clans. Life in the fortress instilled a strong sense of family loyalty and self-reliance; everyone pitched in, whether to repair storm damage, defend against pirate raids, or share resources during lean winters. In the communal fortress, she was raised by her aunts, uncles, and neighbors as much as by her parents.

This idyllic but demanding life came to an end when Doctor Robotnik targeted Fortress Cliff for conquest, attracted to its strategic position and natural defenses. Fiona's family and community resisted valiantly, but were overwhelmed by Robotnik's firepower and forces. In the chaos, Fiona, then 11 years old, was separated from her family and captured along with many other islanders. The loss of her family, whether they were roboticized, killed in action, or otherwise scattered to some unknown fate, left her with the deep and unresolved wound of abandonment.

Fiona's formative years of climbing cliff walls, enduring harsh weather, and relying on her wits helped her survive the brutal conditions of Robotnik's slave labor camps longer than most. However, the violent shattering of her communal bonds and the failure of anyone to come to her rescue planted the seed for her eventual turn to cynicism and self-preservation.