Hollow Technique, Spiritual Technique
Cero (虚閃 (セロ), Sero; Spanish for "Zero", Japanese for "Hollow Flash", literally "Empty Disaster"), also called Meiunbaku (命運 爆 Doom Blast) for it's immense power, is an attack used by Menos, Arrancar, and Visored.
As a standard energy blast, it consists of firing a powerful blast of concentrated spiritual energy at the target. While in most cases it is fired from the mouth, some Arrancar and Visored can fire Cero from their hands, fingers, and other parts of their bodies. This often requires the user to take on a specific pose, though exceptions always exist.
The power, force, speed, and blast area of the Cero is dependent on the strength, spiritual power, and sometimes skill of the user (i.e., the stronger the user, the stronger the attack), and there are some Arrancar who have come up with their own variation of Cero. The charging and firing time for Cero varies greatly, from charging relatively fast to firing it to instantaneously firing one without much charging. Despite the damage it can cause at long range distances, the damage a Cero causes as an explosion is more dangerous when used at close range.