Alina Gray is a sixteen-year-old magical girl from Kamihama City, born in the Sakae Ward and attending Sakae General School as a first-year high school student. She has long, straight green hair with a yellow highlight, often partially tied with a red ribbon in her school uniform, and turquoise eyes. In her school outfit, she carries a small bag of art tools at her waist. When transformed, she wears a rainbow dress with a large black ribbon, black boots, fishnet stockings, and a police-style hat resembling a warden's cap. Her shield-shaped green Soul Gem is located on the ribbon at her throat. Her magical girl design follows a prison motif, with Alina representing the role of the warden.

A self-described artistic genius, Alina is haughty, arrogant, and teasing, often laughing at the misfortunes of others and treating murder as a form of artistic expression. She is erratic and impulsive, quick to anger when things do not go her way, and deeply protective of her art. Her manner of speaking includes English words or phrases delivered with a distinct Japanese accent. Her motivation to become a magical girl stems from a childhood marked by death: at age eight, the deaths of her grandparents and her pet dog sparked a fascination with the transition from life to object. Growing up surrounded by art in her parents' gallery, she began creating works exploring the boundary between life and death. After winning an award for a self-portrait, a judge criticized her work for lacking an external theme, calling it like a dangerous drug and predicting her brilliance would fade by age fifteen. This critique led to a creative crisis. In despair, she destroyed her own artwork and attempted suicide by jumping from a rooftop, intending her death as her final artistic statement. Kyubey appeared, and she made her wish for an atelier where no one could bother her. Surviving the fall, she encountered a Witch and became captivated by its grotesque beauty, which reignited her passion.

Alina has the unique ability to generate barriers and labyrinths at will. Her primary weapon is a cube-like construct resembling a Rubik's cube that can imprison Witches, their Familiars, and entire labyrinths inside small, portable cubes. Her designated Doppel is named Old Dorothy, the Doppel of Fever, which takes the form of a tube and extrudes a special paint called Pathogen Tempera. This paint hardens to create a giant false body for attacking, and anyone who touches it is said to be driven insane. Within the story, she attends the same school as Karin Misono, a junior in the art club, acting as a harsh and critical mentor who occasionally shows a begrudging caring side. As a founding member of the Wings of the Magius, Alina serves as one of its three leaders alongside Touka Satomi and Nemu Hiiragi, though her commitment is to her art rather than the group's ideology. Influenced by theories on the death drive, she believes humanity subconsciously craves destruction and eventually seeks to orchestrate a global catastrophe as the ultimate work of art. Her character arc is defined by a consistent obsession with destruction as an artistic medium, and she shows little to no redemption, remaining committed to her vision of beauty forged from life, death, and despair.