Bella Yaga is a witch who adopts the orphan Erica, known as Earwig, specifically to gain help with her demanding spellwork, declaring she requires "an extra pair of hands." She was once the drummer in a band named Earwig alongside Mandrake and Earwig's biological mother. Her striking appearance includes bright blue, curly hair often tied back for work, heavy makeup, elaborate jewelry, and distinctive mismatched eyeshadow. She wears her usual flamboyant clothing covered by an apron during spell preparation.

Presenting as cold, selfish, and domineering, Bella Yaga imposes arduous chores on Earwig: grinding rat bones, gathering garden ingredients, and cleaning her cluttered, foul-smelling workshop. She denies promised magic lessons, insisting Earwig's tasks are essential for spell components, even demanding actions like eliminating a ballet rival. Though harsh, she provides meals, private quarters, and bathroom access, showing no physical abuse. Her solitary nature surfaces when unexpected physical affection causes her to freeze or appear uncomfortable, hinting at isolation.

Her relationship with Mandrake involves tension, especially during meals where her criticism sparks his anger; their shared past in the band Earwig suggests deeper ties. She strictly forbids music in the house, reflecting unresolved conflicts from the band's end. Her familiar, Thomas the talking cat, aids her spellcasting and later assists Earwig's rebellion. When Earwig enchants her with literal "extra hands," Bella Yaga retaliates furiously with magical worms. This spell fails due to Earwig's immunity, triggering chaos involving Mandrake and shifting household dynamics.

Ultimately, Bella Yaga settles into reluctant coexistence rather than maintaining authority, especially after Earwig's biological mother visits. While still stern, her earlier rigidity softens within the new family arrangements, and she ceases enforcing Earwig's labor demands.