Retroact Rain is a unique phenomenon classified as a form of Waveworn Phenomenon. It consists of condensed Remnant Energy from the Etheric Sea, an energy that records events across time and space. The rain’s defining characteristic is its ability to conjure illusions of past events, projected as Phantoms for those exposed to it. These Phantoms are often tied to strong emotional connections with the affected area, leading to more intense and personalized hallucinations for individuals.

Formation and Stages

Before Retroact Rain fully forms, it goes through three distinct stages:

1. First Stage: The rain appears indistinguishable from regular rain.
2. Second Stage: Water droplets become completely still, floating in midair.
3. Final Stage: The rain reverses its direction, with droplets falling upwards toward the sky.

When the Retroact Rain reaches its final stage, it can project countless Phantoms. On battlefields, such as Jinzhou, this can result in the projection of thousands of Phantoms, including dead soldiers and Tacet Discords. The Phantoms can be given physical form and harmful abilities if the rain is enhanced by the Threnodian’s power.

Phantom Projections and Conditions

For someone to appear as a Phantom in the Retroact Rain, two conditions must be met:

1. The person must have had prior exposure to the Retroact Rain.
2. They must have a deep emotional or situational connection to the area affected by the rain.

In its enhanced state, the souls of those who die within the Retroact Rain become trapped within it. This effect was notably witnessed during the Battle Beneath the Crescent against Ovathrax, three years before the current story, and again in Main Quest Chapter I: Act VI – Grand Warstorm.

Historical and Artificial Research

The Retroact Rain has been extensively studied by researchers driven by personal obsessions, such as reliving past experiences or reuniting with loved ones. The Court of Savantae led many of these studies, with one group attempting to create an Artificial Retroact Rain. This secretive project, funded by a male Fractsidus Overseer, aimed to recreate a "divine miracle" witnessed by its researchers. Despite constructing a remote facility for their experiments, the project was never completed, and all members mysteriously vanished.

Similarities with the Sonoro Sphere

The Retroact Rain shares properties with the Sonoro Sphere, as both are formed from Remnant Energy. While the Sonoro Sphere interacts with external frequencies to shape new realities, the Retroact Rain similarly uses these properties to project vivid memories and illusions tied to the energy's recorded events.

This explains why illusions are always somehow related to those who come in contact with the rain, because the frequencies interact with each other and Remnant energy shapes new consequent reality.

Dangers and Countermeasures

The Remnant Energy within Retroact Rain attracts Tacet Discords, making areas affected by it dangerous. Enhanced Retroact Rain poses even greater threats as it brings Phantoms to life, capable of inflicting physical harm.

Within the last three years, the Academy developed an antidote that minimizes the hallucination effects of the Retroact Rain.