 All hollows have masks attached to their faces and a hollow hole somewhere on their bodies; they also have a tendency to attack those who were close to them in their human lives, which they superficially have no recollection of.Hollows possess individual "reishi" and intensify it through devouring any soul they come across.The 2018 film elaborates that the hollows had played a role in the concepts of the mythological creatures like Yokai.