Corticarte Apa Lagranges reigns as the powerful Red Elder Spirit, bearing titles like Crimson Annihilator, Bloody Duchess, and Crimson Queen. She manifests with six wings, sometimes depicted with eight. Typically appearing as a petite child with red hair, brown eyes, and a large black bow, she transforms into a full-figured adult approximately 170 centimeters tall when her contract partner, Phoron Tatara, plays or sings a Divine Song. This adult form possesses distinct physical proportions, often clad in elaborate attire featuring elements like a slit dress and bridal gauntlet, and grants her enhanced abilities.

Her personality is possessive, moody, and tsundere. She frequently exhibits jealousy when Phoron interacts with other girls, stemming from being entranced by his singing voice during their first encounter. This led her to form a pact ensuring his exclusive devotion. Her possessiveness manifests as protectiveness over Phoron, questioning his actions, and initiating physical contact like holding hands.

One of the eldest spirits in her world, Corticarte was imprisoned in the basement of Torvas Divine Song Players Academy before Phoron inadvertently freed her by singing a Divine Song during his student years; he initially believed their meeting was a dream. She previously held a contract with another Dantist, Kuchiba Kaoru.

Across various storylines, she engages in combat, utilizing her abilities for protection and battle. She shares a past acquaintance with Managariastinockle Lagu Edraikerius, a spirit from the Black series, though altered forms prevent mutual recognition in later encounters. She also maintains a friendship with Eliphas Blanca Albiona, the White Holy Beast spirit.

Her development involves adapting to human interactions through her bond with Phoron, though core traits of assertiveness and emotional volatility persist. Their contract emphasizes mutual dependence: her power activation relies on Phoron's heartfelt music, while his growth as a Dantist is intertwined with her influence.