Archangel Michael

Archangel Michael is an angel who is known as "The Likeness of God". Fiamma of the Right, the leader of God's Right Seat, is aligned with Michael. It is said that the sword Curtana has power equaling the powers of Archangel Michael and that the wielder, the queen, acts as the leader of the angels while the knights themselves act as angels.

Background
Archangel Michael was created by God to defeat the malfunctioning Lucifer. Michael defeated the legions of fallen angels and Lucifer himself, casting them down with the power of his right hand. He then assumed the position that Lucifer formally held, that of leader of the angels.

Michael is said to wield a flaming sword.

Document of Constantine Arc
During her interrogation, Lidvia Lorenzetti says that Michael is the being with the highest-level power and was created to oppose the Fallen Angel Lucifer. Then, she adds that God's Right Seat believe that Michael defeated Lucifer, who sat to the right seat of God, and became the ruler of all the angels, but implies that this might not be the whole truth.

British Royal Family Arc
The events surrounding the British Halloween revolve around the Curtana, a sword which provides a royal wielder with the simulated power of Michael, leader of the angels (with the knights associated with the army of angels and as such, capable of being supplied power from the sword), while in the territory of the United Kingdom, as the focus of a national spell. The circumstances surrounding the sword are explained to Kamijou Touma when he meets Queen Elizard, wielder of the Curtana Second.

Coronzon Arc
During the final battle between the reproduced Mathers and Aleister Crowley, the former manifested the four archangels representing the elements, including Michael, however they were immediately dispelled when Aleister used a spell to banish Uriel, which dragged the others down along with it.

Toaru Kagaku no Railgun SS2: Shopping Mall Demonstration
During the incident at the Russian Shopping Center, Caliche I. Niknosh's cabal made use of Telesma aligned to Archangel Michael and symbols connected to him for a large-scale spiritual item, in the form of a giant wheel snake, with the fact that Michael is also considered a patron saint being suited for their use of Ex Voto.

Abilities
Though Archangel Michael himself has yet to appear, the extent of his power is suggested by his background, the immense powers of fellow Archangel Gabriel and the power displayed by the Curtana, which was drawn from him.

Trivia

 * In the Abrahamic tradition, the archangel Michael is commonly perceived as one of the highest-ranking angels and ranked as the commander of the army of God.