Hecate is a prominent figure within the Crimson Denizen organization known as Bal Masqué. She holds the title of Priestess and is one of the three leaders of the group, forming a part of the Trinity alongside Sydonay and Bel Peol. Her true name is Master Throne. In appearance, she is depicted as a small, pale young girl with short, light blue hair and a seemingly emotionless or inorganic expression. She typically wears a large white cape and a matching hat, and is often seen carrying a staff-like Treasure Tool called Trigon.

Hecate’s personality is defined by a profound sense of emptiness and a quiet, melancholic demeanor. She speaks very little and has a habit of praying, despite having no specific deity to pray to, which other members of Bal Masqué find peculiar. This emptiness stems from a lack of a stable sense of self. Her primary motivation is to fill this inner void, leading her to seek an answer or a purpose for her existence. In the light novels, her personality is described as colder and more feared by her own subordinates, contrasting with her more passive portrayal in the anime.

Within the story, Hecate serves a critical function for Bal Masqué. As the Priestess, she acts as a direct link of communication for the organization's god, the Snake of the Festival. She is also responsible for controlling the movements of Seireiden, the massive floating fortress that serves as Bal Masqué's mobile base. Her role becomes central to the organization's plans involving the Reiji Maigo, a Treasure Tool within the protagonist Yuji Sakai. Because Hecate is a vessel with an immense, nearly infinite capacity for the Power of Existence, she is the key to exploiting the Reiji Maigo's ability to replenish its holder's power at midnight.

Her key relationships are primarily with her fellow Trinity members. Sydonay, the General, shows a great deal of care for her, while Bel Peol, the Strategist, frequently speaks of her potential to become an eternal existence. Her most significant development occurs through her interaction with Yuji Sakai. In the first season, she synchronizes with Yuji to absorb his sense of self in an attempt to fill her emptiness. This process nearly causes a catastrophic release of power when Yuji confronts her, forcing her to acknowledge the void inside herself. In the second season, she creates a faux vessel named Fumina Konoe, a girl identical in appearance to herself, and sends her to observe Yuji. The human memories and emotions Fumina experiences and later returns to Hecate cause a shift in the Priestess, granting her access to genuine human feelings for the first time. This leads to moments of hesitation and confusion, such as when she finds herself unable to harm Yuji and is even shown shedding tears.

Hecate possesses immense power as a Crimson Lord, second only to the Snake of the Festival and the God of Punishment, Alastor. Her most notable ability is an Unrestricted Spell called Aster. This technique unleashes a devastating rain of homing, explosive energy blasts that resemble a meteor shower. She typically activates this spell using her Treasure Tool, Trigon, but she can also cast it without the staff. Other abilities include playing a flute that summons dragons made of blue flame and creating faux vessels, such as Fumina Konoe. She is also highly skilled in close-quarters combat, matching the abilities of the Flame Haze Shana. Her role as a vessel is central to her character, as she can be used in powerful rituals, such as the one that created an "Existence Spring" in conjunction with the Reiji Maigo.