“It’s simple. I distort the flow of power a bit.” The young man shrugged. “Eastern feng shui is the same. The existence of mountains and rivers changes the flow of energy through ley lines and the like. In that case, you can create a ‘ditch’ that draws in the surrounding energy by creating a new mountain or river. It’s the same as how the rainwater will naturally flow toward an irrigation canal and be swallowed up.”
Fenrir was the beast that would devour Odin during the final battle of Ragnarök. The gods had feared him and so bound him and stabbed a sword into his mouth through the lower jaw so he could not close his mouth. When they had, the drool that had flowed from Fenrir’s giant maw had created a large river.
He had used that legend.
By incorporating the same symbols as a river into a location, he created a large “ditch” that swallowed up the massive power of the ley lines. It forcibly swallowed up the magic power that constructed magic and swept it away.

Toaru Majutsu no Index New Testament vol.8 ch.4 pt.9