Angel

Angels (天使) are immensely powerful beings with very volatile existences in the Toaru Majutsu no Index universe. They can be beings of either divine origin, such as the Archangels Gabriel and Michael of Christian doctrine, or artificial existences consisting of masses of highly concentrated AIM fields built-up from the thousands of espers within Academy City. Angels of divine origin get their magical power from a substance known as Telesma.

Appearances
Angels, both divine and artificial, have been described as possessing halos above their heads and various forms of wings manifesting from their backs, some of which such as the case of Archangel Gabriel can reach several kilometers into the sky, as well as speaking in an Angelic language that sounds like high-pitched gibberish to normal humans.

If deemed necessary, like a command from God, or being forced down from Heaven, an angel can acquire a human form. In the Old Testament of the Holy Bible, Angels hid their identities to enter ordinary people's cities and had meals with them. Indeed, as Gabriel can attest, he can hide his being an angel from humans quite easily.

Personality
Vento of the Front explains that Angels in the magic side have no free will of their own and that they are meant to be God's perfect tools, and are often referred to as messengers of God to humanity. Although, they can malfunction and in turn can be called a Fallen angel, or known as demons. According to Stiyl Magnus, Angels and Devils are similar in nature, however, the important thing is who they take orders from.

However, when a divine angel falls from heaven due to the effects of Angel Fall, they can break the orders of God in order to return to Heaven, such as killing humans, despite creating a paradox for God's plans for the Final Judgment, and seemingly have an orderly fashion of thinking. As with the case of Archangel Gabriel under the guise of Misha Kreutzev, who spends his time helping Touma, Tsuchimikado Motoharu and Kanzaki Kaori trying to find the culprit of her fall. Later when Kaori and the others try to prevent him or more appropriately inconvenience him from killing Kamijou Touya who was unknowingly the culprit, Gabriel resorted to destroying the world instead.

The case is somewhat different in the science side however, as evidenced by Kazakiri Hyouka's existence, as she displayed emotions similar to that of humans. However, Hyouka herself is shown to behave as a mindless tool similar to that of angels in Christian lore, after having her Fuse=KAZAKIRI mode activated.

Abilities
As stated angels in both sides are extremely powerful beings, capable of causing great destruction. So much is their power, that their very existence can distort the world. Even a depowered one such as Archangel Gabriel in his first appearance was simply toying with Kanzaki Kaori, a powerful Saint in her own right.

An archangel such as Gabriel has been shown to possess the ability to manipulate any celestial body through the use of "Astral in Hand", allowing it to immediately block the sun by speeding up Earth's rotation. He also displayed tremendous speed, able to move from Russia to France easily and eliminate their forces.

In order to be "summoned" or take a physical form on Earth, Angels must have a medium, or "core", to keep them bound to the Earth. Likewise, if the core that binds them is destroyed their physical form will leave the Earth.

Both divine and artificial angels seem to be weak to Touma's Imagine Breaker as well, as with the case with Misha Kreutzev trying to avoid Touma's right hand, as well as Touma himself trying to avoid touching Kazakiri Hyouka after finding out her true form.

Abrahamic Angels
One notable feature that the angels of the magic side has is their name being chosen by God, which is the purpose for which they are created. As such the names of angels cannot be easily changed, unless a powerful distortion changes these laws of God. Angels are also genderless and is depicted in some Christian lore as having qualities of both male and female.

Angels are also apparently susceptible to Angel Fall, which forcibly casts them down from heaven. At which point, angels will try to get back into heaven, even if it means disobeying the will of God.

An angel's name and attributes are widely referenced by magician's spell chants throughout the story, such as being used as a way to borrow power from when constructing a magic array.

Archangels
Archangel is a term used to refer to angels of higher rank than normal angels, in the Toaru Majutsu no Index universe there are four recognized archangels that are aligned to their own corresponding elements and attributes.

Each member of God's Right Seat derive their powers from the four archangels depending on their alignment after cleansing as much of their original sin as possible.

Archangel Gabriel
Archangel Gabriel (大天使　(ガブリエル)) is an archangel that appears in Toaru Majutsu no Index. He embodies the The Power of God (神の力) and represents the symbol of water which is its attribute, and is the guardian of the moon, the governor of blue, and the protector of the rear side. He is the only true abrahamic angel to appear in the series thus far.

Acqua of the Back is aligned with the archangel. Because of the distortion of the elements, he can bypass the name God has given him and is weaker than normal, even then Gabriel is still more powerful than several other characters combined such as Accelerator and Kazakiri Hyouka.

Other Archangels

 * Archangel Uriel, also known as God's Flame or Fire of God
 * Archangel Raphael, also known as Medicine of God
 * Archangel Michael, also known as Regard of God or The Likeness of God

Fallen angel
Lucifer the Light-Bringer was said to be an angel that was the closest being to be allowed to sit to the right of God, until he malfunctions and causes chaos in one-third of all the angels in heaven, making him rebel against God's will and causing war and becomes a fallen angel. He is later defeated by Archangel Michael who became the ruler of all the angels, and had become a higher being compared to Lucifer even though they were once equals.

Moreover, there is a mention of the Grigoris by Sherry Cromwell as the ones who gave knowledge to humans on how God created Man from clay before the time of Noah, knowledge which eventually gave birth to the golem.

Aiwass
Aiwass, the entity that Aleister Crowley supposedly summoned and the true author of the Book of the Law, has also shown the characteristics of an Angel, possessing a halo above its head and a divine form.

Espers
Accelerator and Kakine Teitoku, the most powerful espers within Academy City, have also shown the characteristics of angels when in their "Awakened" form, or in canon, gaining wings. This comes out of some sort of shift in Accelerator's and Kakine's thinking, like desperation, which gave birth to the Accelerator's black wings. Accelerator also speaks in the language of angels during his first three ''Awakenings".

Artificial Angels
Magic cabals such as the Hermentic Order of the Golden Dawn (Aleister Crowley's former magic organization), seem to have dabbled in creating angels themselves by collecting the formless telesma into a container which is in the image of a person. It is unknown if they had succeeded, though since Aleister Crowley has successfully manage to create an artifical angel on his own, he was most likely influenced by the cabal's methods.

One example of an "artificial angel" is Fuse=KAZAKIRI, the "artificial angel form" of Kazakiri Hyouka, an existence that manifested from the mixing of AIM fields throughout Academy City and resides in the "Imaginary Number District" when not physically manifested. Fuse=KAZAKIRI, an existence that is considered considerably less powerful than an a Christian archangel, has displayed the ability to fire beams of energy that can reach several kilometers in length, project an AIM barrier that protects all those around her, flying at supersonic speeds and manifest a powerful energy sword.

The AIM Burst, an AIM entity product of the Level Upper network also displayed angelical attributes such as a Halo and wings similar to those of Fuse=KAZAKIRI. It should be noted that Kazakiri Hyouka, Aiwass and AIM Burst all had small triangular-prism shaped cores inside their bodies that sustain their existence.

Index Arc
An image of an angel is created by and appears before Index and Tsukuyomi Komoe, as one of the requirements of the spell that will completely heal Index.

Angel Fall Arc
Archangel Gabriel appears for the first time after being casted down from heaven due to Angel Fall. Here, under the name of Misha Kreutzev, Misha tries to help Touma and the others find the culprit, which is later discovered to be Kamijou Touya. Misha is kept occupied by Kanzaki Kaori just long enough for Tsuchimikado Motoharu to completely destroy the ritual location of Angel Fall, and sending her back to heaven.

Kazakiri Hyouka Arc
Kazakiri Hyouka manifests herself for the first time, and later discovers her true existence. It is later revealed that it she is the result of Aleister Crowley's efforts to create an an artifical angel and with the Imaginary Number District, an Artificial Heaven.

Academy City Invasion Arc
Due to Vento of the Front's invasion of the city, Aleister Crowley activates Fuse=KAZAKIRI in order to test it out on her. Here, she displays complete and utter domination on the invading forces outside the city. Even then, Hyouka still retains some sort of control as she protects civilians from Vento of the Front's attacks during her battle with Kamijou Touma.

Meanwhile, Accelerator partially awakens during his fight with Kihara Amata, and kills him using the power of his black wings.

Battle Royale Arc
Accelerator fights off against the leader of SCHOOL- the Number Two esper Kakine Teitoku. Kakine reveals three pairs of seraph wings during the battle, which allowed him the fully utilize his Dark Matter ability. By stabbing Yomikawa Aiho, who had just arrived with Anti-Skill, Accelerator was enraged to the point where he awakens, with massive black wings made of Dark Matter. After seeing this, Kakine also fully awakens and gets enlarged wings, but was instantly defeated by Accelerator.

DRAGON Arc
Accelerator soon encounters Aiwass, a higher dimensional super-being, who is an artificial angel that had Last Order as its core of existence. Accelerator used his black wings and fought against Aiwass, but was completely defeated by the being, who had golden wings that sprouted from its hair.

World War III Arc
The leader of God's Right Seat Fiamma of the Right summoned Archangel Gabriel with the Star of Bethlehem. Gabriel was told to retrieve the lambskin document that was kept by Accelerator. Aiwass soon expands the AIM field to Russia, and allows Fuse=KAZAKIRI to go fight against Gabriel. Accelerator also joins the fight, and they hold Gabriel back. Due to being the strongest link to the Power of God, Acqua of the Back takes away 1/3 of Gabriel's power, rendering him vulnerable and not responsive to Fiamma's commands. Together, Fuse=KAZAKIRI and Accelerator manage to defeat Gabriel. Soonafter, Accelerator fully awakens, giving him a halo, and turning his wings from black to white.

Level Upper Arc
An AIM Burst appears after Kiyama Harumi loses control of the Level Upper Network, and threatens to attack a nuclear facility. It is later destroyed by Misaka Mikoto, after Uiharu Kazari plays the Level Upper treatment program all over Academy City, removing the monster from the network and the power to reform itself.

Trivia

 * Agnese Sanctis' Lotus Wand has a metallic figure of a seraph mounted on top of it, when Agnese activates the wand, the figure opens up all of its six wings allowing Agnese to use its power. It is assumed that there are other classes of angelic beings in the universe, however, it is unknown what their positions or hierarchies are, if they are higher or lower than the Archangels themselves.