The final attack was fired.

Technically, Kamijou Touma was unable to see it. In all likelihood, only a highly-advanced
Rishi would be able to see it and any inexperienced person who attempted to look would
be blinded. Vishnu had always been closely associated with the sun and it went without
saying what would happen to anyone presumptuous enough to look at the core of the sun
with the naked eye.

However, a scene did appear in the back of Kamijou’s mind.

He saw the moment when he had certainly “died”.

To ensure she killed him with her crossbow of certain death, Magic God Othinus had
sacrificed her own body. She had hidden the attack behind her so that it would pierce
through her and her target.

Marian was supposedly attempting to take revenge on Othinus, but instead of focusing on
Othinus herself, it seemed she had prioritized making the girl watch someone important
to her die.

As long as she could kill Kamijou Touma, it did not matter what happened to her.

And so Kamijou immediately took action.

“Marian!!!!!!”

He pushed down her small brown body and threw himself on top of her just before the
brilliant beam of light shot down from overhead. As he was lying on his stomach, the boy
could not see what it was, but he felt an intense burning pain stab into his entire back. It
felt like a red-hot metal plate was being pressed down on him.

He screamed at the top of his lungs.

The swarm of locusts flying defenseless through the air evaporated. Even the flame-
controlling black giant was brought to its knees by the tremendous light.

Kamijou and Marian were tossed into the air.

Her fight had likely ended as soon as this final attack was launched, so she had passed out.

-Shinyaku Toaru Majutsu no Index Volume 10 Chapter 13 Part 6