Endorsi Jahad is a major character in Tower of God, known for her role as a Princess of Jahad and a Regular climbing the Inner Tower. Her background is defined by a ruthless upbringing that shaped her into a formidable and complex individual. Born over three centuries ago, she was not born into a Great Family but was instead adopted by a couple from the Middle Area belonging to one of the Ten Families, specifically the least significant branch known as the house of fallen nobles. This family sought to gain power by producing a Princess of Jahad, adopting talented girls and forcing them through a brutal training regimen. Endorsi was initially the weakest among the candidates, so low in rank that she was not even allowed to eat at the dinner table and was forced to eat stale bread on the floor while watching others feast. Realizing that only strength mattered, she used her innate talents to systematically defeat and eliminate all the other adopted girls, thereby securing her position as the sole candidate and earning the right to become a Princess. Her adoptive parents were later killed by a figure known as the Snake Charmer.

Endorsi's personality is a direct result of this harsh past. She presents herself as haughty, proud, and exceptionally confident, often declaring herself a goddess or national treasure to emphasize her status and power. She is calculating, ruthless, and unafraid to betray or eliminate others to achieve her goals, a trait she demonstrated during the first test on the Floor of Tests where she, along with Rachel and Akryung, eliminated nearly two hundred other examinees. Despite this cruel exterior, she has a more vulnerable and human side that emerges over time. She is deeply concerned with her appearance, fashion, and weight, frequently dieting and dressing in expensive clothes to maintain her image as a perfect idol. The author has described her character concept as a normal modern girl who is stressed about her looks, wants to hear she is pretty, and has yet to fully mature. She enjoys her popularity and the attention of the media within the Tower, though she finds the paparazzi annoying, and she has been featured on magazine covers for promising Regulars.

Endorsi's primary motivation initially is to climb the Tower and enjoy the privileges of being a Jahad Princess, a title that forbids her from marrying or having romantic relationships. However, her journey is profoundly altered by her key relationship with the protagonist, Twenty-Fifth Baam. Initially indifferent to him, she agrees to join his team and becomes his close-combat trainer on the second floor. Through Baam, she begins to experience genuine friendship, loyalty, and care for others, slowly breaking down the cold, self-serving persona she built to survive. Her feelings for Baam evolve into a deep romantic interest, and she eventually kisses him, declaring that the memory should belong only to the two of them. She is fiercely protective of him and was deeply depressed after believing he had died, later going to great lengths to confirm that Jue Viole Grace was indeed Baam. Another critical relationship is with Anak Jahad. Though they initially clash violently and are often at odds, Endorsi reveals that she truly wants to climb the Tower with her. When ordered by a Ranker to kill Anak, Endorsi defies the command and chooses to fight alongside her instead, solidifying their unique, combative, sister-like bond. She maintains a good working relationship with Khun Aguero Agnis and Shibisu, often working together to help Baam, though she frequently bosses the latter around. She holds open hostility toward Rachel, viewing her as a weak, manipulative traitor for her betrayal of Baam.

Within the story, Endorsi serves as a powerful ally and a key member of Baam's group. Her role highlights the dark and competitive nature of the Tower, as she is a living product of its brutal system. Her physical abilities are among the highest of any Regular; she is considered unmatched in terms of raw physical strength and combat skill among her peers. She specializes in hand-to-hand combat and can also control Shinsu, the mystical energy of the Tower. The author has stated that she and Baam form the strongest pair among Regulars, combining his Shinsu control with her physical power. She possesses a distinctive small horn on her right temple, a non-human racial trait often mistaken as part of her hairstyle.

Endorsi's character development is central to her arc, as she gradually transforms from a self-serving Princess who embodies the cutthroat values of the Tower into a person who values friendship, loyalty, and defies the very system that created her. She questions her role as a Princess and shows a willingness to challenge Jahad's authority, particularly when protecting her friends, proving that she is far more than the cold, ruthless girl she was forced to become.