Index Librorum Prohibitorum

Index Librorum Prohibitorum (禁書目録インデックス Kinsho Mokuroku (Indekkusu), lit. "Index of Prohibited Books") is the titular deuteragonist of the light novel and anime series A Certain Magical Index, also making a few appearances in A Certain Scientific Railgun. Commonly known as Index, she is the main female character of the series and is considered the main heroine of the Magic Side. She is a member of Necessarius, the 0th Parish of the English Puritan Church and has a Photographic Memory. She holds within herself 103,000 magical texts known as grimoires.

She is voiced by Yuka Iguchi in the Japanese version of the anime and Monica Rial in the English version, the latter of whom also voices May Chang, Mirajane Strauss and Yukari Sendo.

Appearance
Index is small in stature, has a petite build, and, much to her chagrin, a flat chest. She is very childish, as in the anime she always wants to get Touma's attention with many annoying ways. It can be assumed that she is very young and sort of annoying child. She has thigh-length, silvery-white hair, and large green eyes. She is also often seen wearing her Walking Church, a white, modified nun's habit with gold highlights. It is an accurate replica of the Holy Shroud of Turin and offered Index ultimate protection from most attacks, however, it was destroyed by Touma's right hand. She still wears it, though safety pins are now needed to hold it together. She is noted by Touma to be a "gaikokujin" (foreigner), and it is likely that her nationality is English.

Personality
She is often elated by things that an adult would find mundane and is slightly ignorant and curious of modern technology. She is usually gentle and polite with people and has a kind nature, as shown when she picked up a stray kitten and took it home, although Touma initially refused. She can be easily irritated in a similar manner to how a child reacts to something they don't like- especially when it comes to Touma, who usually ends up angering her in some way as a consequence of his own bad luck. He is often bitten by index as punishment. She also has an extreme appetite as shown when she met Accelerator and forced him to spend all of his money treating her to food. Index has taken a liking to the anime Magical Powered Super Android Girl Kanamin and once cosplayed as her. She has strong feelings towards Touma and even confessed her love after knowing Touma lost his memories because of her, however he avoided answering by changing the subject of the talk since he has no idea about what kind of feelings he used to have with Index.

Abilities
Her sorcery name is Dedicatus545, "The dedicated lamb protects the knowledge of the strong" (献身的な子羊は強者の知識を守る Kenshinteki na Kohitsuji wa Kyōsha no Chishiki o Mamoru?). As the vessel for 103,000 magical books, she is unable to use conventional means to cast spells; instead, she can only use abilities which intercept opponents' spells.


 * Photographic Memory (完全記憶能力 Kanzen Kioku Nōryoku ?, lit. "Capablity of Perfect Memorization"): She is capable of perfectly memorizing anything, such is one of the reasons why she was chosen as the vessel for the 103,000 grimoires, magic books that are poisonous to the mind. This made Yamisaka Ouma wonder if Index is even human.


 * John's Pen (自動書記ヨハネのペンJidō Shoki (Yohane no Pen) ?, lit. "Automatic Writing"): According to Index, she is incapable of magic, however, when under John's Pen Mode, she is capable of accessing the grimoires in her memories, including once performing a complex magical ritual that healed her of all her injuries. It is unknown whether or not she was capable of performing magic before losing her memories. Her self-protection system will use the "Feather of Light" to force a reset on Index's own memory should a manual reset fail to be performed.

After Touma negated the runic symbol that was meant to destroy her mind, while in John's Pen Mode, she was capable of using several very powerful spells:
 * 1) St. George's Sanctuary (聖セントジョージの聖域 Sei (Sento) Jōji no Sei'iki?, lit. "Sanctuary of St. George"), a high class defensive spell which distorts space-time.
 * 2) Dragon's Breath (竜王の殺息ドラゴン・ブレスRyūō no Satsuiki (Doragon Buresu)?, lit. "Killing Breath of the Dragon King"), a high class offensive spell that has the same amount of power as the legendary dragon of Saint George. This spell casts a beam of light at the target, destroying everything in it's path. It has been shown to have very long range, like when it destroyed Academy City's satellite that housed the supercomputer, 'Tree Diagram', in outer space. It is also shown that the first level of this spell is enough to surpass the cancelling speed of Kamijou Touma's Imagine Breaker and at it's second level, is enough to blow away Innocentius with ease. The after-effect of this spell is the Feather of Light.
 * 3) Eli Eli Lama Sabachthani (神よ、何故私を見捨てたのですかエリ・エリ・レマ・サバクタニKami yo, naze watashi wo misuteta no desu ka?, "Lord, why have you forsaken me?") - Is a powerful anti-Christian spell which throws a powerful bloody-red beam of light.
 * 4) Scarlet Stone of Pexjarva (ペクスヂャルヴァの深紅石 Pekusujaruva no Shinkuseki?) - This spell causes the bones in the target's feet all the way up to his knees to feel a deep pain started to swell up. This feels like the pain from the joints between the bones being forcibly stretched apart. This invisible attack seems to be coming up from the floor and seeped into target's body from there.
 * 5) Sulfur Rain will Scorch the Earth (硫黄の雨は大地を焼く Iō no Ame wa Daichi o Yaku?) - A area spell attack which throws about 50 arrows appearin from above which strucks down like guillotines piercing and burning through the target. Just an arrow alone is enough to turn stone into dust.
 * 6) During her stay on St. George's Cathedral while she was being restrain by Stiyl Magnus she grows crimson wings which is said to be angelic wings, with them was enough to dissipate Innocentius and blow his user away with just flapping them.
 * 7) She also displayed the ability to summon legendary weapons and artifacts creating multiple copies of the same and use them to attack, all of them 'being able to suffocate the enemy just by floating in the air', some of the weapons mentioned are:
 * 8) The Sword the Harvest God Freyr (豊穣神フレイの剣 Hōjōshin Furei no Ken?) or Sword of Victory, the magic sword of the god from the Norse Mythology, which fights on its own "if wise be he who wields it" and was stated its wielder has never suffered defeat.

She can also cast two other magical abilities that don't consume any mana energy whatsoever:
 * Spell Intercept (強制詠唱スペルインターセプト Kyōsei Eishō (Superu Intāseputo)?, lit. "Force Chant"), it uses notarikon codes to hijack the spell formula that the caster has been conjuring in their head and causes the magic to go berserk or be outright cancelled. Index used this ability against Sherry Cromwell's golem and to save Last Order from the computer virus that forced her to manifest 'Fuse=KAZAKIRI'.
 * Sheol Fear (魔滅の声シェオールフィア Mametsu no Shō (Sheōru Fia)?, lit. "Voice of Defacement"), is an ability in the form of choir that points out and impeaches the contradiction of the basis of the religion or theory of magic that has been cast and causes a break down in the enemies mind. Although this can be bypassed if the intended target cannot hear it when the Agnese Force nuns jabbed their own ears to block off the sound.

List of Books in Index
There are 103,000 grimoires hidden within Index's memory, however there are only a few instances where the names of several books have been explicitly stated. Strangely, fictional grimoires in reality are real and are part of Index's representative grimoires in the series.

Trivia

 * It is a recurring gag for Index to bite Touma whenever he has inadvertently annoyed or irritated her in some way, occurring even in serious situations or in front of important persons.
 * Index is still wearing her Walking Church, even though it has lost its powers.
 * Index's 'Dragon's Breath' is one of the few magical attacks shown so far that is able to surpass Touma's Imagine Breaker's cancelling speed.
 * Index is still the only girl to have confessed to Touma, however, Touma avoided answering by changing the theme of the conversation because since he had lost his memories, he had no idea about what kind of relationship he used to have with Index.
 * In Episode 5 of the Anime "Boku Wa Tomodachi Ga Sukunai", a character named Maria (Who has the same seiyuu(voice actor) as Index and is a sister) wears an outfit strikingly similar to Index's.
 * Index is also the first and only girl known to kiss Touma (by the cheek) when she intended to bite him during the Daihasei Festival Arc.
 * Index's bust size has increased a little bit as evidenced in one of the illustrations of Volume 16.
 * Touma has pointed out that she is a sleep walker, and that will always tuck into the futons of others if she is just left alone. This is the main reason of why Touma locks himself in the bathroom every night.
 * During the Angel Fall incident, Touma and Index found out that Index has her own Academy City ID, though neither remembers having applied for it. In the novel Touma thought it was possible using sophisticated equipment to obtain data like fingerprint, retina scans, voice imprint etc., though he doesn't know why anyone would do this. It is implied Aleister Crowley was the one responsible after making an arrangement with the Anglican Church to keep Index inside Academy City. Also, in episode 15 of the anime, Index's ID picture showed for some unknown reason Index holding a green onion. It is currently unknown what the intentions of J.C. Staff was on this matter. Probably a reference to Vocaloid's Miku Hatsune.
 * Episode 13 of Mayoi Neko Overrun! featuring Umenomori Chise (who has same voice actress with Index) commenting how Takumi the main character born with misfortune and how Fumino possess right hand that negate luck using Index like voice.
 * According to the interview on Kazuma Kamachi featured in "Toaru Majutsu no Index no Subete", the author states that Index is the one whom he want to choose as his lover among all Index characters.
 * In the fourth season of the Anime "Zero No Tsukaima", the female lead, Louise, as well as several other characters, wear an outfit that is identical to Index's. Also, Louise has a flat chest, and is known to hurt the male lead, Saito, when angered by him.
 * In an unofficial interview, the creator of the series had admitted that Inder herself is actually based off of a real life girl that he once knew. She had perfect memory like Index in the series and was very kind. Unfortunately, she died at the age of 17 due to a brain tumor so he made Index in honor of her memory.