Explanation of a Saint

Saints are and existence called 'Child of God' and are powerful individuals on the Magic Side. Less than 20 of them exist in the world. Saints hold the ability to call upon God's power which endows them with superhuman physical strength, incredible speed, healing, capacity to channel larger amounts of mana compared to normal magicians, and superhuman senses. The structure behind their power is based on Idol Theory where a replica of a more powerful being or item can also gain a tiny portion of the original's strength. Humans are said to be made in the image of God and Saints are said to be a higher replica that can bring out more strength. Therefore Saints possess an innate special bodily characteristics that allows them draw out a certain percentage of the Son of God's power. As Saints are still human, they have a limit to using the power created through Idol Theory with their own power. Moreover, if Saints used their power at 100% the high pressure would cause the Saint's body to self-destruct.

“Though there hasn’t been any specific information, he obviously has the strength worthy of a member of God’s Right Seat and what seems to be the power of a Saint, so it’d be great if we can get the Priestess’s assistance.” The Priestess that she was talking about was Kanzaki Kaori. She was one of the less than twenty Saints in the world, and had managed to survive a fight against a real archangel. That was truly one achievement she could brag about.
(Toaru Majutsu no Index Volume 16, pg 15)

“Acqua of the Back. I believe I have introduced myself before.” God’s Right Seat. And at the same time, he had the abilities of a Saint.
(Toaru Majutsu no Index Volume 16, pg 52)