Excess magic use has numerous ways of backfiring, most commonly exploding. Or uncommonly, it could have interesting side effects none could have predicted. So imagine what blasting an evil moon goddess with the mother of all rainbows could result in.
A door opens and a lone man enters. The way back is gone and all that's left to do is march forward. Will he break? Or will he fall? Perhaps one should think before they jump. But the choice is gone. No turning back know, let's see what he can do.