The Holy Office of Index (教皇庁禁書目録聖省 Kyoukouchou kinsho mokuroku seishou) or Index (禁書目録聖省 Indekkusu) for short is the largest magical organization in the world of 11eyes. The Catholic Church in Vatican serves as its headquarters.
Index's main objective is to keep the world in their control and eliminate everything considered heretic by Catholic Church standards. For them, Lieselotte Werckmeister, who defies their belief and wishes for the world's destruction, is considered as the top priority threat. Ironically enough, their crusade in 1209, which destroyed Béziers and its entire population, is the determined factor that gave birth to Lieselotte.
After World War II, Index was believed to have been closed down, but the appearance of Ursula of the Bookshelf in Ayamegaoka in 2009 proved that the organization had simply been working on the shadows.
Although unknown to ordinary people, Index has been secretly taking action and manipulating the world to maintain peace and balance; therefore, Index's name is well known in the world of magi and sorcery users. Even the Onmyouji clan of Kusakabe is aware of the organization's existence. However, Index's way of doing their job is also known to be very rational and ruthless. Shuu Amami himself states that Index is simply the tyrant of the supernatural world who will eliminate all supernatural threats indifferently. It was Index who was responsible for the destruction of the Kuroshida clan, a clan of Japanese western magi some time before World War II.
Around 1945, the Witch of Babylon, Lieselotte, headed for Japan; Index's intelligence reported her movement and suggested that she was planning something big. Due to political problems at the time, Index could not mobilize a massive force. Therefore, the head of Index, Johanna sent Georgius of the Rainbow of the Fourteen Saints and his subordinates, a team of well trained and highly skilled members to kill her. However, both Georgius' group and Lieselotte mysteriously disappeared after the fierce battle. Without any traces of Lieselotte left, Index categorized her as eliminated.
Some time later, Index assigned Agatha of the Silver Cross to keep watch on Ayamegaoka and report anything out of the ordinary. However, Agatha was kidnapped around 2009, prompting Index to send Ursula of the Bookshelf under the name 'Shiori Momono' as her substitution. On September 17, having received a report from Shiori that Georgius' team reappeared as hostile, Index gave a Royal Order to Shiori to execute Georgius and his subordinates on sight for treason. It is believed that, according to Shiori, had she reported Lieselotte's existence at Ayamegaoka to Index, another crusade would have taken place and the entirety Japan would have most likely been wiped off from the face of the planet.
Johanna is the founder and highest official Index, who also have the title Pope besides the one who reigns in the Saint Peter's Basilica. She is addressed as Her Eminence. Her personal secretary is Camerlengo Chiara, who has a sisterly relationship with Shiori.
The Fourteen Saints (聖省十四聖 Seishou Juuyon Sei) are the official highest ranking apostles of Index and also the strongest. In Hollow Mirror Field arc, the previous Saints were revealed to be:
- Acacius the Plunderer
- Barbara of the Lightning
- Blasius of the Holy Tree
- Catalina of the Wheel
- Christophorus the Iron Fist
- Cyriacus the Exorcist
- Dionysus the Unfading
- Erasmus of the Blue Flame
- Eustachius of the Illusion
- Georgius of the Rainbow
- Giles the All Loving
- Margarita of the Holy Cross
- Pantaleon of the Silver Blade
- Vitus of the Holy Beast
In charge of the Research Department is Sophia Measley, an apostle who joined around the end of 1945. She is described as a genius but also a mad scientist with strange fetish. She is also responsible for the creation of the artificial bodies for Georgius' family line.
The underground library is a hidden branch of Index's system which few magi know about. According to Shuu, Hieronymus of the Holy Pen, the librarian of the Vatican's underground library is an official of higher ranking than the Saints.
- Main article: Punishment Squad
The Punishment Squad is a special task force of Index, led by Georgius. The squad was officially known as having been wiped out in the battle against Lieselotte, but in fact they continued their duty as the Black Knights and was later killed off by Kakeru Satsuki's group.
- Ursula of the Bookshelf: also known as Shiori Momono, Ursula is the completed ultimate weapon of Index. She was sent to Ayamegaoka to investigate the disappearance of the town's previous curator. She quit Index in 2010, but still keeps in contact with Sophia Measley. In Resona Forma, it was revealed that she could only be allowed to return to Ayamegaoka if she dismissed herself before Johanna.
- Agatha of the Silver Cross: Agatha was Ursula's rival for the seat Margarita. She was originally appointed as the curator of Ayamegaoka but mysteriously disappeared without a trace. It is revealed in Hollow Mirror Field arc that she was one of the victims of the dopplerganger incident.
- In the anime, the Holy Office of Index is nearly the same organization as in the game according to Shiori, but the fact it's partly because of their crusades which lead Lisette's hatred for the world was never mentioned. Moreover, Johanna's existence and Thule weren't mentioned, probably because of the fact that Shiori died in the final episode, and she never came back to Index.
- Georgius is the only saint who has ever made an appearance in the series. Christophorus of the Iron Fist was just mentionned for having given the Warhammer to Samson. Shiori and Agatha of the Cross, an other apostle, was in competition for Magarita position.
- It is implied that Sebastianus and Samson were ancient Saints too.