Jibril

is the youngest and strongest of the Flügel race. Her love towards knowledge started even before the declaration of the Ten Oaths. She opposes the book sharing law created by the Council of Eighteen Wings and left Avant Heim, her homeland, to win the National Library of Elchea from the previous king in a game. When Sora heard what happened to the library, he challenged Jibril in order to gain knowledge of the other kingdoms. When she lost the game, she became Sora and Shiro's servant since she had bet everything she owned, including herself, claiming that knowledge was worth her own life. However, she was allowed to keep the library and maintain it although she must now share it with the rest of Imanity. Thus, Jibril took the siblings as her masters and over time, she began to understand and accept Sora's belief in the potential of humanity. Unlike Steph, Jibril is happy to become the siblings' underling, and is shown to have grown feelings toward Sora.

According to Azriel, Jibril was given the gift of imperfection by Artosh and therefore named the "Exceptional unit". This gift is what Artosh believed would allow Jibril to find the answer to the Flügels' continued existence should he disappear (which was, in fact, the case).

Appearance
She has long purple-pink hair that reach down to her knees and two white wings protruding near her hips. Her pupils are purple surrounded by a gold iris but a cross shape appears in her pupils when she is focusing on a task (such as performing a spell). Her ears are wing-shaped and she also has a halo over her head. She usually has her midriff exposed and wears a long skirt. She has also a slim and well-endowed body. She has the physique of that of a 17-18 year old but in actuality is much older. After unleashing her ultimate attack, her appearance reverts to that of a young girl due to the magic recoil. Her three sizes are from above, 88, 55, 85.

Personality
She seems to be soft spoken and polite, but she can also be incredibly condescending to other races of the Exceed below her own, as shown when she indirectly insults Stephanie Dola and when she refuses to apologize to Fiel Nirvalen for wrecking havoc, also when told she had to lick Fiel's feet she refused saying she would not lick a 'mere' elf's foot. She has a great love for knowledge and gets easily excited at the prospect of gaining new knowledge, such as when she drooled over Sora's tablet after seeing the vast information it contained. Despite her initial arrogance, she has a high sense of honor while playing games, as she doesn't like cheating, or being cheated. She tends to remember the "good old days" before the oaths were established and when everything could be solved by killing, in a rather disturbing way, somewhat showing her sadistic personality.

She is also perceptive, being able uncover the weakness complex formula of Elf where none of her sister can do so, and also figure out Steph's feeling to Sora.

Unlike Steph, Jibril fully embraces her servitude to Sora and Shiro, going so far as to address them both as "Master". Throughout the anime and light novel, Jibril's feelings for Sora seem to grow, despite stating she's not supposed to have the feeling called love. Jibril first stated her feelings in Episode 10 wondering even though it's supposed to be humiliating that she licked Fi's foot, if she takes it as a order from the master she gets excited, questioning whether it could be love, before Sora interrupted her. Despite this, in Light Novel Volume 4 Jibril has expressed a willingness to merge a part of Sora's soul with her own to attempt to create a hybrid, essentially showing a willingness to bear his child. Later on, in Light Novel Volume 5, she confesses to Sora that she can finally understand love (or her perceptive of it) and has fallen in love with him.

History
Jibril is the last and most powerful Flugel created by the Old Deus Artosh and served under him until his demise. During the war of the gods she destroyed the capital of Elven Gard with a single spell known as "Heaven's Strike", which resulted in Jibril not being able to use Magic for 5 years. Afterwards Jibril stole all the books in Elven Garde despite the Elves best attempts to prevent this. Due to the loss of so many books, the Elves lost a considerable amount of magic and, as stated by Fiel, it took over 800 years to regain all the lost powers.

Sometime during the Great War, while embarking on one of her solo campaigns, she came across an Ex-Machina named Shuvi. Ex-machina heads were extremely rare prizes amongst the Flugel, because at the time there was an unspoken rule to never provoke the Ex-machina lest one seeks ruin. However, Jibril was confident she could take down Shuvi, so she had no choice but to retaliate. Despite her greatest efforts, Shuvi was ultimately defeated and killed by Jibril. However, Jibril did not escape unscathed, as she had used Heaven's Strike against Shuvi and lost all of her magic power.

After Artosh was defeated and the war concluded, Jibril lived in the Flugel city Avant Heim for some time. However with the passage of the Book-Sharing Law, she decided to leave as she did not agree with it and did not want her books passed along freely. Sometime after she challenged the Imanity King for the rights to his library, which she easily won. Jibril then stayed at her library until she was challenged by Sora and Shiro, where she lost in a game of Materialization Shiritori. In accordance with the bets for the game, she swore her very being to Sora and Shiro. Although not requested by Sora and Shiro, Jibril would go on to accept the siblings as her new masters, seemingly having replaced Artosh.

Jibril would then follow the siblings on their quest to reach Tet, the one and only God. This included helping them in their quest to acquire the Werebeast nation, Dhampir and Seiren Nation, and even a trip to her homeland, Avant Heim. Along the way, she has been documenting their actions in her own book.

Strengths
As the final unit and most powerful individual of the Flügel race, her massive strength was hinted at by Azrael who stated that, were she to assist Sora and Shiro in playing a game of tag against 100 other Flügel, the match wouldn't be considered a competition at all. It is unknown what her full capabilities are (disregarding Heaven's Strike). However, parting a pathway through the sea to Oceande is apparently a representation of 5% of her full strength. She is also seen being in close proximity to a blast from a hydrogen bomb, and emerging unaffected. Her speed is also incredible, capable of moving, maneuvering, and reacting well pass the speed of sound with ease. All of her senses are unrivaled, for example she was capable of perfectly seeing and locking on the elves base, even though she was miles above in the sky, it was night and there was smoke everywhere.

As a member of the Flügel race she is absolutely immortal, possessing an infinite life span: immune to all diseases, illnesses, disorders, toxins, impurities, and physical and/or mental interference; she is entirely self-sustained; will never age (always remain in her physical and mental prime) and is immune to aging abilities; she is virtually invulnerable to all harm as shown when she was shot by the elves and she only fell out of her flight course, but was otherwise physically unharmed, and even if she is injured she can regenerate from any injury. As the most powerful Flügel her immortality, invulnerability and regenerative capabilities are vastly superior to any of her race.

As a Flügel she possess a limitless level of intellectual (memory, calculation, learning, creativity, IQ, etc.) and cognitive (observing, deduction, tactical analysis, multitasking, combat, movement, etc.) proficiency that is of the highest level in existence, an extremely high IQ and intellectual capacity. This is shown in the ability of the Flügel  to start “stealing” all knowledge after the ten pledges are established as an alternative to their practice of taking heads, since absorbing the knowledge of all others is the same as taking their head. Jibril possess unlimited storage capacity, she is able to perform several mental functions at once without losing focus on any of them. Her mind allows her to instantly recall specific information with incredible speed and perfect accuracy. She is able to store everything that she experiences and retrieve it immediately without the typical human pause for thought. The speed of her thoughts augments her analytical ability so that she is able to make snap decisions about her surroundings and create complex scenarios at high speed. She is able to track the probability of an event by piecing together stored data, and is able to perform multiple tasks at once by allocating a portion of her brain to each task. She can use her mind to replay an event that occurred during the war she has seen, play a game, and focus on battling an opponent simultaneously without any one task distracting her from another. She was told Sora that she can speak, read, writes, understand, and communicate in any and all forms of languages. The knowledge she has gathered during her millennia of existence are incredibly vast. However it is not perfect or infallible, as she lost to Sora and Shiro. She's also a very competent mage, capable of using spells to teleport herself, Sora, Shiro and Steph to any place she can see or that she's been to previously. She's also capable of phasing through walls at will.

It is said that Jibril has once used a spell called "Heaven's Strike," also called "Airstrike," which had completely annihilated the capital of Elven Garde. As a drawback, she could not use any magic for 5 years. In Light Novel Volume 5 of the novels she uses the power again but does not suffer from any recoil as she was in an illusionary world where her magic power was unlimited.

As the "final unit" of the Flugel, Jibril's power is capable enough to kill a Gigant, a Dragonia, and a Phantasma on separate solo campaigns. However, her failed attempts to do so were twenty nine times more (simply put: out of 90 attempts, 3 were successful).

Weaknesses
Due to being a Flügel, Jibril is very dismissive of other races below her own and her confidence in her own knowledge. This in turn causes her to overlook the potential threat posed by the said races. This is no more evident than in her game with the siblings, that even with the knowledge from her examination of Sora (that the siblings weren't from Disboard), she still regarded Sora and Shiro with barely concealed scorn, but was intrigued by the discovery.

Sora mentioned that Jibril lost in her game of Materialization Shiritori because of her arrogance. For example, the game could have ended in Jibril's favor in the first move where Sora and Shiro called upon a Hydrogen Bomb. Instead Jibril shielded them from the blast because, as Sora predicted, it would have been boring for her.

Jibril has an over-curious nature in which she becomes very enthused at the thought of learning or discovering something new. As such, she can be bribed in exchange for knowledge she doesn't know (although finding something she doesn't know is challenging as she has been learning for thousands of years).

Whenever Jibril uses Heaven's Strike, her body regresses to that of a young girl.

Trivia

 * The author stated that Jibril is the Arabic reading of Gabriel, and that the name is not from the hentai Djibril – The Devil Angel.
 * She is the first Flugel to serve a human.