丑の刻参り Ushi no koku mairi is one of the most famous and dreaded black magic spells. It takes place between 1:00 and 3:00 in the morning, during the hour of the ox. This is the period of darkest night, when the border between the world of the living and the world of the dead is weakest. During this hour, evil spirits are at their greatest power... Read more: http://yokai.com/ushinokokumairi/