Reisen (虚閃 Hollow Flash) is a Shinigami technique that mimics the Cero used by Hollow. It functions on the same principles, the user gathers their Reiyoku into one spot and forms a sphere that they fire a beam of energy out of. The difference being that the gathered Reiyoku is that of a Shinigami, not a Hollow. As a general rule a Visored's Reisen is stronger than their Cero due to their natural Reiyoku being Shinigami. Conversely an Arrancar's Reisen tends to be weaker than their Cero.