As he thought that, Fiamma purposefully removed his left hand that was pressing against his wound to prevent blood loss. At the same time, a small explosive noise exploded out. The blood spewing out showed the outlines of a large invisible arm. It was his third arm. He could no longer control that power with his own will, but now he could fight.

“I believe this to be futile.”

Aleister Crowley did not seem to make any real preparations for a fight.

[...]

Fiamma was not even sure if he had come to understand even a fragment of that, but that was why he had the following thought.

He could not allow it to be trampled on.

Even if he had to face a true monster, he could not allow the world that boy had risked his life to save to be trampled on any more.

It was obvious at first glance who won and who lost.

Two forms clashed and one of them fell from a slope of the mountain.

Silence returned to the snowy plains of Russia.

The victor glanced down the slope and spoke as his body dissolved into the air.

“…You tried to explain that right hand, Imagine Breaker…and even The One Who Purifies God using only something at the level of Christianity. That was your mistake.”

Toaru Majutsu no Index Vol.22 epilogue