ArchAngel Gabriel is an archangel that appears in the Toaru Majutsu no Index main storyline. Being a divine entity and classed as an archangel, makes Gabriel one of the most powerful non-human characters in the story.
In fact, Gabriel is called the The Power of God (神の力, Kami no Chikara?) and according to Kaori, Gabriel rules over 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. Acqua of the Back of God's Right Seat is aligned with Archangel Gabriel, which allows him to do feats similar to that of Gabriel when it comes to manipulating water.

Gabriel featured an androgynous appearance, and is classified as being depicted as both male and female; despite this, Gabriel features breasts, and has feminine features as well, though shows no obvious genitalia.

Gabriel has pure white skin, which has golden lines adorned all over its body in an intricate pattern mostly concentrated on its upper torso, forearms, upper legs, and lower ankles. Interestingly, the golden lines meet in the middle of Gabriel's breasts into a kite-like shape, bearing the symbol of the cross (this can also be seen on Index's Walking Church). These golden lines are also present on peculiar flaps that are on Gabriel's wings. These flaps can be seen attached on Gabriel's head – which seems to simulate hair, forearms, legs and waist – which seems to simulate coattails. On top of Gabriel's head is a blue halo, inside the ring is an inner circle where three arrow-shaped lines jut out, slightly beyond the outer ring in differing directions.

Like most of its body, Gabriel's eyes are white and seem to sport no visible iris and pupil.

Though not normally depicted with wings, Gabriel sports wings made of crystallized water through the use of its powers.