Mandrake is an extremely tall, lanky figure with distinctive pointed ears, often mistaken for horns. He wears thick circular glasses that deliberately obscure his emotions, contributing to his mysterious demeanor. His typical attire is a purple robe and pants with a faint floral pattern layered over a white button-up shirt. When angered, he undergoes a dramatic transformation: his eyes spark with rage, veins appear on his forehead, and dark smoke emanates from his back. He grows in size, develops dark scales, sprouts claws on his hands and feet, and his clothing tears, shifting to orange and black hues as the smoke intensifies to cover his body.

Easily upset, he wields significant power within the household, often isolating himself and resenting disturbances. Despite his volatile temperament, he possesses underlying good intentions and is the first to show kindness to the protagonist, offering warmth during shared meals. He exhibits a low tolerance for weakness or subordination, manifesting through aggression and intimidation when challenged.

Formerly the pianist for the rock band Earwig, his hair was then long and dark purple. After the band disbanded, he became an author, though his books consistently receive poor reviews. He now resides with his former bandmate, Bella Yaga; their relationship remains strictly cynical and pragmatic, devoid of friendship.

Within the household, Mandrake magically seals all entrances and exits, preventing departure. He commands small, bat-winged demons that enforce his rules, such as pushing books onto intruders in his study. His presence looms over daily life, with Bella Yaga warning against disturbing him. He displays unexpected kindness during dinner when the protagonist compliments his cooking. Newspaper clippings and music records in the house link him to the band Earwig and the protagonist's mother.