Distortion (世界の歪み Sekai no Yugami , lit. "Distortion of the World") is a phenomenon that occurs when Humans are devoured for the Power of Existence.
When a Crimson Denizen devours a Human for their Power of Existence, the world undergoes a "shift", leaving behind a permanent mark on the area. Those sensitive to the Power of Existence, such as the Flame Haze can feel their presence. Both the Flame Haze, and Crimson Denizens create Torches to cover up the presence of this Distortion.
Areas that gather a great amount of Distortions eventually come to be referred as Maelstrom of Warfare, such as Misaki City. When Asiz utilized the City Devourer to convert the city of Osterode into Power of Existence, he created a massive Distortion which attracted the attention of the Flame Haze all around the world.
However, what causes the Distortion is not missing Power of Existence as believed by the majority of the Flame Haze, but the conversion of this existence into an unstable state, a truth known to The Four Gods of Earth. And the location of this Distortion is not in the Human world, nor the Crimson World, but in the realm between these two: the Abyss. Eventually, should the Distortions continue to increase in number, a storm that would engulf both the Human world, and the Crimson World would be created.
The Midnight Lost Child taps into these Distortions to replenish the Power of Existence of the bearer. Later, Snake of the Festival with the help of Dantalion uses the Treasure Tool to tap into all the Distortions at once so he could amass the Power of Existence that was needed for the creation of Xanadu.