Lunar Rain is yellow rain that falls after events in Kolton.
Background
The people of Kolton initially think that the Lunar Rain is a miracle. They talk about how invigorating it is to be out in the Lunar Rain. When the Liberation Force first discovers Lunar Rain, it has a positive effect on people with Lunaglyphs, increasing their stats. Later, however, Edward becomes sick from it. After meeting Kiriya, it is revealed that Lunar Rain increases the power of Lunaglyphs until the bearer can no longer contain it. The power consumes them and they become Vermiforms. The transformation can only be stopped by Lunar Suppressant. After that event, when the Liberation Force is in Lunar Rain, there is a chance someone will become a Vermiform.