Fiamma of the Right used Gabriel to augment his five senses.

“So it’s like this, huh...?” He spoke in a bored voice. “So this is my enemy.

[...]

The form of an angel was basically a mass of energy, they had no physical body. More
accurately, their bodies were not composed of physical matter. Fiamma, who was linked
to Misha, was suddenly dealt a blow through his five senses.

-Toaru Majutsu no Index Volume 21 Chapter 8 Part 7


Fiamma and Gabriel’s senses were linked and Gabriel’s abilities of perception were quite
different from those of a human. Even if the parchments had been in the target’s pocket,
the archangel could obtain the magical information recorded on them.

-Toaru Majutsu no Index Volume 21 Chapter 8 Part 9