Sasha Kreuzhev operates within Annihilatus, a specialized unit of the Russian Orthodox Church dedicated to eradicating non-existent spirits and supernatural threats. Her name presents ambiguity through romanization and Russian linguistic conventions—"Sasha" functions as a unisex diminutive for Alexandra or Alexander, while her surname "Kreuzhev" bears a masculine suffix, fueling speculative debate about her gender despite consistent female portrayal. She appears approximately 13 years old, with long curly blonde hair often concealed by her hood, and bangs typically obscuring her eyes. Her distinctive attire—a revealing, translucent one-piece garment restrained by leather belts across her torso and limbs, complemented by metal braces on her ankles, wrists, and waist, a red hooded cape, and matching pointed shoes—was forcibly designed by her superior, Vasilisa, as a personal hobby. This outfit causes Sasha profound embarrassment and attracts frequent derisive remarks.

Sasha communicates with formal, structured phrasing, organizing thoughts numerically using prefaces like "My first question:" or "A supplementary explanation:" She maintains a tactical, pragmatic approach during missions and exhibits marked distrust toward those she deems "dangerous," a response shaped by Vasilisa’s persistent sexual harassment. This distrust triggers aggressive reactions, such as attacking Kamijou Touma with a nail puller during a medical exam. She dislikes luxury foods like sweets or gum, though a temporary taste for chewing gum emerged during her possession by the archangel Gabriel. Defying regulations, she consumes brandy during work hours.

Her chronological involvement initiates with the Angel Fall incident, where her body hosted the archangel Gabriel—who operated under the alias "Misha Kreuzhev." Gabriel exploited her form to locate the spell’s instigator, wielding archangel-level abilities like celestial manipulation. Post-resolution, a massive residue of Telesma (angelic mana) lingered within her, rivaling the Holy Mother’s capacity. This residue induced unexplained physical tremors and heightened magical sensitivity, alerting her to nearby active spells or spiritual items. The Russian Orthodox Church placed her under observation, unaware of the cause.

During the Anglican–Russian Orthodox prewar conference, Sasha accompanied Vasilisa to London, visiting the Necessarius Women’s Dormitory to unofficially assess allegiances. Her attire provoked repeated reactions, prompting her to mutter criticisms labeling the Church a "perverted organization." Later, in the British Royal Family Arc, Vasilisa warned her of the Church’s order to capture her due to the Telesma. Vasilisa renounced Church contracts and aided Sasha’s escape, during which Vento of the Front intervened, guiding her to the Elizalina Alliance of Independent Nations for sanctuary despite Sasha’s fears of provoking Russian aggression.

In World War III, Fiamma of the Right targeted Sasha to exploit her residual Telesma, misaligned with Archangel Michael’s attributes after Angel Fall. Captured alongside allies like Vento and Lessar despite resistance, she was imprisoned aboard the Star of Bethlehem. She later collaborated with Kamijou Touma to disrupt Fiamma’s control by inscribing a magic circle into the fortress. During this conflict, Gabriel briefly repossessed her body before Touma neutralized the threat. Post-war, Sasha resumed duties in the Russian Orthodox Church. She reappeared in New Testament as security for Patriarch Krans R. Tsarskiy at a United Nations anti-Gremlin conference in New York, admonishing Vasilisa for straying from orthodox beliefs. Her role expanded during Gremlin’s Tokyo invasion, though operational specifics remain limited.

As a combat magician, Sasha wields British-made spiritual tools resembling torture implements—hammers, screwdrivers, saws—strapped to her waist. These generate Wall-level destructive force, enabling her to breach heavy doors and walls. She demonstrates proficiency in protective magic, such as insulating against extreme cold, and situational adaptability, though she favors physical tools over complex spells. Her physiology uniquely permits full archangelic hosting; Fiamma noted her potential strength surpassed Accelerator and Hyouka Kazakiri at half-capacity. The Telesma residue also amplified her sensitivity to magical energy.

Sasha’s relationship with Vasilisa defines much of her conflict: the harassment and degrading outfit shape her defensive behavior and cynical view of their organization. Others’ interactions frequently fixate on her attire—Touma called it "ridiculous," while Sherry Cromwell questioned its seasonal practicality. During her Elizalina escape, Vasilisa offered replacement clothes Sasha rejected as equally humiliating. Her alliance with Vento of the Front was pragmatic, born of mutual need despite friction over clothing choices.