Esel Borgnine, also known as Ethel Borgnine in some sources, is a twenty-nine-year-old woman who appears in the anime The Legendary Hero is Dead! as a famous thief and wanted criminal. Her appearance is distinctive, characterized by long, flowing hair that she often uses to cover her left eye, and she is consistently depicted wearing gloves. Her background is deeply intertwined with that of the protagonist, Touka Scott. Three and a half years before the main events of the story, she met Touka in the northern continent. Although she initially refused his request to become her apprentice due to her status as a fugitive, she was moved by his determination and agreed to mentor him. During their months-long journey to Elvania, she taught him everything she knew about setting traps and wilderness survival techniques, establishing a foundational master-apprentice relationship.

In terms of personality, Esel is portrayed as cunning, determined, and highly confident in her own abilities. While she possesses a sharp and calculating mind, she also reveals moments of unexpected gentleness and a hidden sweetness. Her strong survival instincts are balanced by a serious commitment to her own moral code, which leads her to hold a distinct belief that necromancers are the ones who should guide the world down the correct path. Despite her criminal background, she demonstrates a fierce loyalty to those she deems worthy, especially her former student, Touka.

Her motivations and role in the story undergo a significant shift following a traumatic event at Hell's Gate three months prior to the series' present timeline. Witnessing the opening of the gate caused a drastic change in her intentions, leading her to betray the hero's party she had been allied with and join forces with the necromancers in an assassination plot. Her plan was thwarted by Touka's cleverness, and she was defeated in battle. Upon learning that the true current hero is none other than her own apprentice, Touka Scott, she decided to change sides once more and cooperate with his group. Although she continues to hold her conviction that the necromancers' way is the correct one, she temporarily left Touka's side after the battle in Elvania. However, she ultimately chose to return and fight beside him again at the Hell's Gate after discovering that the Kingdom of Roselia, a former ally, planned to use its overwhelming power to rule the world through fear.

Esel is a highly capable magic user with a magic level of eight, which classifies her as a high-ranking sorceress. She specializes in necromancy, which she performs using specific magic crystals for that purpose. In combat, her primary skill lies in deploying complex, multi-layered traps to neutralize her enemies. Despite her expertise, she has been shown to have a surprising degree of carelessness, and her overconfidence has occasionally allowed Touka to outwit her. She also harbors a dark secret that explains why she always wears gloves: she has transplanted the left arm of the Demon King onto her own body, granting her immense and unusual power.