The Radiance of Extinguishment is a technique that was employed by Nine the Phantom in her final moments. Little is known about this technique, but when used, it gave Nine enough energy to be able to activate the Corpus Sepulcro: Requiem and bind Izanami despite having been mortally wounded by Ragna the Bloodedge. 
Given the name and application of the technique, it is possible that it can only be used when one is near death. Izanami called it the life-force of those who live.
- BlazBlue: Central Fiction, Story Mode, Episode 010, Chapter 082