Cordelia Glauca is one of the four primary members of the Milky Holmes detective agency. She possesses blonde hair, teal eyes, stands 161 cm tall, weighs 47 kg, and celebrates her birthday on December 19, making her 17 years old. Cordelia exhibits strong delusional tendencies, particularly fixating on maintaining perceived healthy relationships within Milky Holmes, often imagining herself as the group's protective elder sister.

She harbors intense phobias of dark spaces and sea cucumbers. Exposure to darkness triggers extreme reactions, causing her to lose rationality and exhibit destructive behavior or a perverted personality shift, such as forcibly disrobing Hercule Barton during confinement. Under extreme stress or despair, she manifests unusual capabilities, projecting hypnotic flower field delusions onto others, often with yuri undertones, or displaying bursts of physical strength and reflexes, like parrying sword strikes with a ceramic plate.

Her supernatural ability, a "Toy," grants extraordinary sensory perception, enabling her to detect imperceptible smells, sounds, and visual details, such as reading a swordsman’s movements or seeing through illusions, though this power remains mostly inaccessible after its early loss in the series. Outside detective work, she sketches, frequently depicting Milky Holmes in idyllic flower fields despite limited technical skill.

Her competence varies across media portrayals. Anime adaptations often emphasize her comedic failures and cloudcuckoolander traits, while other portrayals, particularly in games, showcase her as a capable combatant proficient in hand-to-hand confrontations against antagonists like Stone River or Arsène. She serves as an emotional catalyst during group low points, using her flower-based delusions to alleviate collective despair, and occasionally advances plots through sensory insights during rare Toy recoveries.