Phenomenon Intervention is an ability possessed by Observers that allows them to alter one possibility into another.
Observers, and by extension Onlookers, have the ability to manipulate phenomena as they see fit.
There are multiple realities, and Observers can overwrite certain realities with others within reason. In the BlazBlue: Continuum Shift recap in BlazBlue: Chrono Phantasma Extend's Anthology, an example is given with Ragna the Bloodedge. If Ragna dies in reality 'A', then it is overwritten with reality 'B', where he does not, then a Phenomenon Intervention has occurred. There are an infinite amount of possibilities, such as the one where Ragna did not die, but is injured. Only the Takamagahara System and Amaterasu Unit are capable of overwriting major phenomenon such as this.
Amaterasu can overwrite any phenomena, be it minor or large, whereas the Takamagahara System can only overwrite large phenomena, and Observers can only overwrite minor ones. Clavis Alucard and his daughter Rachel Alucard are capable of Phenomenon Intervention that can stop the flow of time itself, leaving only them and their targets capable of movement in the frozen time-space.
Certain beings are immune to Phenomenon Intervention. Chrono Phantasma (Phantoms of Time), like Rachel, are immune to the Phenomena Interventions of Observers. Chrono Phantasma (Those Who Should Not Exist) are immune to Observation, and thus immune to Phenomenon Intervention as well; unlike the Phantoms of Time, however, this also affects those who close to them. The Sword of Destruction: Kusanagi gifts its wielder the ability to be completely immune from any Phenomenon Intervention.
The act of 'intervening' on existences and phenomena (events). It refers to one with a 'will' Observing phenomena.
- BlazBlue: Chrono Phantasma Extend, Story Mode, Anthology - Extra Story: Continuum Shift
- BlazBlue: Bloodedge Experience - Part 1, Chapter 1 - Contact
- BlazBlue: Bloodedge Experience - Part 2, Chapter 9 - Interference
- BlazBlue: Central Fiction, Library Mode, World #001
- BlazBlue: Central Fiction, Library Mode, World #002
- BlazBlue: Central Fiction, Library Mode, Power #021