Power is a Fiend, specifically the Blood Fiend, inhabiting the corpse of an unknown human female. Her appearance features long hair shifting between blonde and pink across media, red and yellow cross-patterned eyes, sharp fanged teeth, and light red horns protruding from her head; these horns grow larger and multiply when she consumes excessive blood. She wears the standard Public Safety Devil Hunter uniform untidily, often leaving her jacket half-off and using breast pads to enhance her bust. In her full Blood Devil form, she transforms into a taller, multi-limbed humanoid with a predominantly white body, a dark pointed head, an exposed ribcage filled with intestines, and clawed limbs. Initially, Power exhibits a highly self-centered, deceitful, and chaotic personality. She constantly boasts about her superiority and lies compulsively to evade consequences, readily blaming Denji for her own transgressions. She demonstrates poor hygiene, rarely bathing or flushing toilets, and openly admits to lacking loyalty, aligning only with the winning side. Her motivations are purely self-serving, focused on personal gain or survival, and she displays a cruel imagination, fantasizing about oppressing humans through extreme taxation. She consumes any meat—including human or zombie flesh—while rejecting vegetables. An early exception to her selfishness is her unconditional love for her pet cat, Meowy (also called Nyāko), whom she initially intended to fatten for consumption but grew genuinely attached to, even sacrificing Denji to save it. Power's character develops significantly through relationships. After Denji rescues her and Meowy from the Bat Devil, she moves into Aki Hayakawa's apartment with Denji. Their initially contentious dynamic evolves into a sibling-like bond marked by constant bickering but mutual reliance. Traumatic encounters, particularly with the Darkness Devil in Hell, leave her with severe PTSD, making her terrified of darkness and solitude. During recovery, Denji and Aki assist her with basic needs like eating and bathing, revealing vulnerability beneath her bravado. She gradually develops genuine loyalty and compassion, notably for Denji, whom she later identifies as her "first friend." This culminates in her defying Makima's control to protect him; though tempted to betray Denji to regain Makima's favor, she instead sacrifices herself to save him, an act opposing her core self-preservation instincts. Her abilities center on blood manipulation. As a Fiend, she heals and empowers herself by consuming blood, with excessive intake causing physical changes like enlarged or additional horns. She solidifies her blood into weapons such as hammers, knives, spears, and scythes, and deploys hidden blood traps for surprise attacks. She can also manipulate others' blood through direct contact, though she finds this difficult. In her full Devil form, she gains enhanced strength, speed, and durability, executing techniques like the "Thousand Tera Blood Rain," generating thousands of blood projectiles. After Makima kills her, she temporarily revives as the Blood Devil through Denji's blood, gaining expanded powers like manipulating enemies' blood internally to disrupt regeneration. Her final act involves a contract with Denji: she transfers her blood and life force to heal him in exchange for his promise to find her reincarnation and befriend her anew. Outside the main series, Power appears in the spin-off light novel *Buddy Stories*, investigating disappearances at an inn alongside Denji, highlighting her comedic traits and chemistry with him.