“Norse mythology talks of decorations that make the wearer’s body invisible. Marian can likely use something like that as she can create the weapons of the gods,” said Thor. “And there is one common factor among all magic that makes the user invisible. The magician that uses it has no way to know if they have actually been rendered invisible or not. …Ever since she entered the plaza, I’ve been adding some ‘seasoning’ of my own to the landscape so it will fail. That means you won’t lose sight of her.”

Toaru Majutsu no Index New Testament vol.5 ch.4 pt.11