First off, the rain is a sort of Jesus for this whole religion revolving around it. And it seems to seek out those who are worthy to drench them and make them disciples of it. There also appear to be three main characters. Spike himself, a mysterious other purple
Person, and a green person. The green one seems to want to "own" the rain, but one of the three explains that the green one will end up killing it eventually due to being unfit for having it. But then, a post by dpine that reads "he's gone..." in green font loads me to believe that the green one is an antagonist of sorts.