Spinel Fean began as a human alchemist for the merchant association The Star God's Pavilion. She became a prominent member of the mercenary group Parabellum after being rescued during the First Group of the First Expedition led by Ogarou, choosing to remain with them following their stay at Trient. Her appearance is that of a cool intellectual beauty, featuring medium-length black hair usually in a ponytail and frequently depicted wearing glasses.

Her personality blends diligence with a calm, analytical approach. She developed sincere gratitude and romantic feelings toward the group's leader, Rou, after he prevented her assault. This relationship deepened, leading to her pregnancy discovered around Day 109. Due to expected birthing complications, Rou performed a cesarean section to deliver their daughter, Nicola. Spinel embraced motherhood, accepting and cherishing her child.

Professionally, she served as Parabellum's chief alchemist, utilizing her expertise across roles including Merchant, Alchemist, Magical Item Maker, and Mother of Demons. Her skills encompassed potion crafting, trading, and advanced alchemy magic. She earned the title "Consort of Demon ■■" on Day 119, later clarified as "Consort of the Overlord" or "Main Wife of the Demon God."

Her daughter Nicola, distinct among Rou's offspring for being fully human, did not experience rapid aging like her half-siblings. This required ongoing supervision, though care from Nicola's step-siblings allowed Spinel to balance her duties. Despite her typically composed demeanor, she displayed intense passion during interpersonal conflicts, such as a notable disagreement involving a Dryad that caused tension.

Her relationships center primarily on Rou as her lover and Nicola as her daughter, within the dynamics of Parabellum.