As a member of the prestigious House of Gremory, Rias embodies a blend of kindness and strength. She is compassionate and nurturing, especially towards her servants and those she holds dear. However, beneath her gentle exterior lies a fierce protector; she reacts with intense anger and even violence when her peerage or loved ones are insulted. This fiery disposition underscores her deep-seated aversion to cruelty, as seen in her disdain for individuals like Marius Tepes, who abused his own sister, and her decisive actions against the Fallen Angels—Mittelt, Dohnaseek, Kalawarna, and Raynare—who mistreated Issei. Rias also empathizes with Sairaorg and his mother, Misla Bael, understanding the pain inflicted upon them by the Bael clan.

Proud of her lineage, Rias prefers to be recognized simply as herself rather than as the heiress of the Gremory name. Her choice to live in the human world stems from a desire to be seen as Rias, free from the weight of her title as the Crimson-Haired Ruin Princess. This yearning for normalcy led her to grow disenchanted with romance, as many suitors seemed more interested in her family’s status than in her as a person—until she encountered Issei, who changed everything.

Rias views Issei as her special person, and her jealousy flares when other girls are around him, revealing a more possessive side. Though she possesses the mature demeanor of a woman, she often exhibits the emotional intensity of her true age, growing frustrated when girls flirt with him. While she typically maintains her calm and composed nature, Rias loses her poise whenever she witnesses someone, especially Akeno, attempting to seduce Issei.

Rias enjoys playfully teasing Issei and Asia, but she firmly establishes her claim over Issei, making it clear to all that he belongs to her. The Gremory family, known for their deep emotional bonds, reflects Rias’s own capacity for affection; she is unabashedly open with Issei, comfortable enough to share intimate moments, including sleeping nude beside him. Despite their seductive allure, both Rias and Akeno retain a certain innocence regarding love, often reverting to their youthful selves in Issei’s presence.

After becoming Issei’s girlfriend, Rias blossoms with newfound confidence, gradually accepting his dream of a harem and even allowing the other girls to spend time with him. While she still occasionally feels jealous—especially when Issei doesn’t dedicate enough time to her—her love for him remains unwavering. As Issei’s official girlfriend and later fiancée, she earns the title of “Legal Wife,” a role that requires her to navigate the feelings of Issei’s other admirers and maintain balance among them. Ravel observes that the responsibilities of being the “Legal Wife” weigh heavily on Rias, often more so than on Issei himself, as she strives to manage the emotional complexities of each relationship. Rias shares a dependence on Issei similar to Akeno’s, as she can become disheartened and lose her drive when he is injured or in danger, often rushing to his side at the first hint of trouble.

Rias holds her older brother, Sirzechs, in high esteem, despite his somewhat overprotective tendencies, as she deeply cares for him. In her childhood, she admired him while grappling with feelings of inferiority, relying on his support.

Passionate about participating in Rating Games, Rias dreams of becoming a champion, aiming to defeat the reigning titleholder, Diehauser Belial, with her peerage’s support. Though she is undeniably powerful—exceeding many High-class Devils and displaying potential to reach Ultimate-class status—she wrestles with an inferiority complex, particularly when comparing herself to the strategic prowess of Sona or the raw strength of Sairaorg. Nonetheless, her talent for identifying and recruiting skilled individuals for her peerage shines through; during the Azazel Cup, she garnered praise for her ability to scout and recruit exceptional allies, including Crom Cruach and Vasco Strada. Rias is also a gifted negotiator, successfully persuading Rossweisse to join her team with offers of improved working conditions, and appealing to Vasco Strada’s warrior spirit to entice him to participate in the Cup.

Rias is fiercely competitive, particularly after her defeat in her first Rating Game against Riser, driving her determination to win, whether in sports or battles. Her upbringing, spoiled by her father, Zeoticus, and her brother, Sirzechs, has cultivated a hint of impatience and a touch of selfishness within her. She indulges in shopping, a passion that often leads to reprimands from her mother, Venelana, and sister-in-law, Grayfia, due to her extravagant spending habits.

In her childhood, a peculiar incident instilled in her an instinctive fear and aversion to camels after being hit by one while teasing it. This fear is so profound that the residents of the Gremory territory ensure that camels are kept at a distance, despite their family’s historical association with the creatures.

Thanks to her education from Souji Okita, Rias has developed a deep admiration for Japanese culture and history. She revels in collecting Japanese souvenirs and was particularly ecstatic during her school trip to Kyoto, though she became pouty and frustrated when unable to explore the city to her satisfaction. After high school, she even founded a Japanology club, further cementing her passion for all things Japan.

Rias Gremory, the second child of the illustrious Gremory family, became the heiress of her clan when her older brother, Sirzechs, ascended to the position of Satan Lucifer, relinquishing his claim to the title. This transition marked a significant turning point in her life, as she was soon thrust into an engagement with Riser Phenex, a match that would shape much of her early experiences as a Devil.

From a young age, Rias faced unique challenges, including a traumatic encounter with a camel that left her with a lasting fear of the creatures. After teasing the animal, she was attacked, resulting in a phobia so intense that even images of camels can provoke her anxiety. This irrational fear is humorously juxtaposed with the Gremory family’s emblem, which features a camel.

Before the events of the series, Rias expanded her peerage by reincarnating several key members: Akeno Himejima, Koneko Toujou, Yuuto Kiba, and Gasper Vladi. Her journey with Akeno began when she rescued her from impending death at the hands of her own Himejima clan. Akeno had accidentally ventured into the territory of Heinrich Cornelius Agrippa, and Rias, acting as her savior, formed a bond that blossomed into a deep friendship.

Koneko’s introduction to Rias’s life came under dire circumstances; she was saved from execution by Rias’s brother, who then entrusted her care to Rias. The duo later welcomed Yuuto, who tragically perished during the “Holy Sword Project,” and Gasper, who was killed by vampire hunters. Each reincarnation reinforced Rias’s resolve to build a loyal and capable peerage, each member handpicked to enhance their collective strength.

Two years prior to the series, Rias enrolled at Kuoh Academy alongside Akeno, Sona, and Tsubaki. Together, they revitalized the defunct Occult Research Club, with Rias taking on the role of president. This club became a sanctuary for her peerage, a place where they could gather, strategize, and grow stronger together.

During their second year, Rias and Akeno embarked on a school trip to Kyoto, an experience Rias cherished despite its shortcomings. Unfortunately, their lack of a well-structured itinerary meant that they missed visiting key sites, like the Nijou-jou, leaving Rias feeling disappointed. Her frustration boiled over at the railway station, where she was seen stomping her feet in exasperation, a rare glimpse of her youthful temperament.

Later that same year, the Occult Research Club organized a haunted house for the school festival, showcasing their creativity and adventurous spirit. Rias took the bold step of employing real ghosts to enhance the experience, enlisting the help of a friendly youkai to assist with decorations. However, this decision backfired spectacularly, resulting in significant trouble with Sona, who reprimanded them for their reckless choice to involve actual supernatural beings in their festivities. This incident highlighted Rias’s adventurous nature and her willingness to push boundaries, even at the risk of drawing ire from her peers.

Through these formative experiences, Rias emerged not only as the heiress of the Gremory family but also as a leader who valued her friends and allies, determined to forge her own path while navigating the complexities of her dual identity as a Devil and a young woman.

Crimson Extinct Dragonar (深紅の滅殺龍姫クリムゾン・エクスティンクト・ドラグナー, Kurimuzon Ekusutinkuto Doragunā):
Also known as the Crimson Dragon Princess of Annihilation, this formidable armor is a powerful combination technique created through the synergy of Rias and Issei. By harnessing Issei’s Red Wyverns, Rias synchronizes their auras, allowing the Wyverns to envelop her in an elegant, female counterpart to Issei’s Scale Mail. This armor not only amplifies Rias’ natural abilities but also grants her access to key powers likeBoost,Transfer, andPenetrate, enabling her to escalate her combat prowess until she reaches her limits. The Crimson Extinct Dragonar embodies the bond between Rias and Issei, showcasing their teamwork in battle.

Forbidden Invade Balor the Princess (禁夜と真闇の滅殺獣姫フォービトゥン・インヴェイド・バロール・ザ・プリンセス, Fōbidun Invueido Barōru za Purinsesu):
Known as the Beast Ruin Princess of the Forbidden Night and True Darkness, this awe-inspiring technique is a collaboration between Rias and Gasper. In this form, Gasper melds into his own shadow, merging it with Rias’ to envelop her in an aura of profound darkness. The result is a striking transformation where Rias appears as a dark beast resembling a human, cloaked in a deep red aura of destruction, complete with a third eye featuring a crimson pupil and ten majestic wings. Drawing inspiration from Sairaorg’s Balance Breaker and enhanced by her Crimson Extinct Dragonar, this form allows Rias to freeze opponents in time using her third eye and navigate through shadows at will. Her Power of Destruction is significantly amplified by the dark energy, granting her control over her own attacks, including altering their trajectories. While still in its unfinished state, this transformation exceeds even Satan-class power, allowing Rias to devastate vast urban areas with ease.

Galatine II (ガラチン II, Garachin II):
A magnificent crimson sword bestowed upon Rias as a divine blessing from Heaven following her engagement to Issei, Galatine II serves as both a powerful weapon and a symbol of their bond. Designed specifically for a Devil, this sword is capable of delivering devastating strikes, harmonizing with Rias’ demonic powers to enhance her combat effectiveness. Rias has expressed her intention to pass down this cherished weapon to their future children, signifying the deep legacy of strength and love within the Gremory family.

Rias Gremory’s equipment not only amplifies her already formidable abilities but also reflects her relationships and personal growth throughout her journey. Each piece serves as a ament to her strength as a warrior and her unwavering spirit as a leader.