Yogiri Takatou

A high school student who gets trapped in the alternate world with Tomochika Dannoura. He has a power that he has kept hidden most of his life, the power to force instant death.

His true form is that of an eldritch entity that exists outside of spacetime and can best be described as the physical personification of the end of all things. His instant death ability is less a power and more him selectively enacting the concept of his being upon other entities.