Lilith is the ancient progenitor of Yuko Yoshida and founder of the Dark Clan, her existence spanning approximately 4,000 to 5,000 years. Millennia ago, conflict with the Light Clan led to her imprisonment within a clay relic known as the Founding Ancestor Statue. This sealed statue journeyed across ancient civilizations like the Orient, Egypt, and Mesopotamia, allowing Lilith to weave mystical bonds and expand her lineage. Her magic waned around 2,000 years ago, severing her connection to the outside world until her consciousness resurfaced ten years before the story's main events. This reawakening coincided with Yuko's demonic awakening, enabling Lilith to communicate through Yuko's dreams and assign missions focused on breaking the family curse and reviving the Dark Clan.

Physically, Lilith mirrors an older Yuko but possesses tanned skin, long wavy blonde hair, a broken right horn, and stands just 144 centimeters tall. In modern times, she favors casual sweatshirts or tracksuits adorned with humorous slogans like "My blood sugar level is dangerous." While sealed, she manifests as a clay haniwa figure with one broken horn, perceived as comical. Lilith exhibits a cheerful, lively demeanor with egotistical leanings, delighting in teasing, boasting, and modern comforts like cola. Despite her self-proclaimed title "Witch of Eternal Darkness" and occasional mischief, she remains fundamentally good-hearted and incapable of true malice. Paradoxically, she harbors a fear of darkness stemming from her prolonged pitch-black confinement.

Her abilities focus on dream manipulation and subconscious interaction, though her seal restricts these powers primarily to Yuko's dreams. She can recreate physical offerings placed near her statue within her dream space. Telepathic communication via the statue becomes possible as her seal weakens. She briefly materializes in the real world by possessing vessel dolls—homunculi crafted by characters like Sion Ogura and Momo Chiyoda. Early vessels were small or deformed Yuko replicas. Later, life-sized vessels built from residual materials permitted activity for up to seven days, albeit with extreme fragility. A Dragon Orb embedded by the water god Mikazuchi granted prolonged presence, conditional on daily collection of 9kg of trash from local rivers to avoid penalties. Lilith also possesses deep knowledge of magic, demon history, and academic subjects, demonstrated when she outperformed Momo on exams while controlling Yuko's body.

A switch at her statue's base, activated under specific conditions, allows temporary possession of Yuko's body, triggering full-body soreness in Yuko. Initially disabled by Momo, the switch was later reactivated by Yuko. Lilith shares a mentor-like bond with Yuko, affectionately nicknaming her "Shamisen" (a blend of "Shamiko" and "ancestor"). Other characters treat her with casual irreverence, including Seiko Yoshida who nearly sold the statue online. Despite this, she maintains generally amicable ties with magical girls like Momo and Mikan Hinatsuki, serving as an unconventional grandmother figure. Local children sometimes deride her as "Gomi Aneki" (Trash Big Sis) during her river-cleaning tasks.

Her narrative arc involves gradual integration into the human world despite physical constraints. Initially confined to dreams and statues, acquiring vessel bodies—especially post-Dragon Orb—facilitates sustained physical presence, marked by comical vulnerabilities. She evolves from a spectral advisor into a quirky participant in daily life, engaging in modern activities like visiting hot springs or designing revealing costumes for demons and magical girls. Her legacy as the Dark Clan's founder remains central, driving her efforts to guide Yuko while reconciling her ancient origins with contemporary absurdities.