User blog comment:SpiritedDreaming/RWBY: Attack on Kevin Tower Defense Game/@comment-27803627-20160830172224/@comment-28288412-20160830175658

I could very well be wrong but that is how I see it.

After every other Grimm is dead we can start killing Kevin, if another month starts then we have to kill the Beringei that spawned before we can damage Kevin again.