it was an illusion

At that time, a thin Western sword made of something like particles of light mercilessly
pierced through Stiyl Magnus’s shoulder and into his chest as he stood within St.
George’s Cathedral in England. The sword was the sword of the harvest god Freyr. It was
a spiritual item that moved automatically and surely stabbed into its opponent’s vitals.
It cut through Stiyl’s collarbone and ripped through thick arteries and organs.
The expression on the girl named Index’s face remained frozen.
Stiyl’s movements stopped.
And in that time, multiple attacks continued on.
Another two swords stabbed into Stiyl’s back and waist and blood red wings swung
down as if to finish him off. The attacks were simply overwhelming. The repeated
attacks crushed human flesh while also causing fatal damage to the life force that was
the source of magic power.
However, Index’s expressionless face tilted ever so slightly to the side in confusion.
The multiple blades and wings had definitely slid into Stiyl’s body. However, there was
no other change. It had been too smooth. No blood was shed and no flesh was crushed.
The human body was not cut apart as easily as a spoon dipping into yogurt.
Her conclusion came too late.
By the time she realized it was a magical trick, the next move had already been taken.
“It is a mirage. It’s a common method,” said a voice behind her.
She then noticed something odd in the area of her spine.
Immediately afterwards, an explosive noise as if from a strike of lightning exploded out.
Stiyl had activated the restraining rune card he had put on her.
Index’s backbone creaked as it bent like a bow.

- Toaru Majutsu no Index Volume 22, Chapter 11 Part 3