Ceridwen definately knows (she seems to actually be taking a much more active role in destroying it than he is. She was the one who let Tebryn live again in order to bring the End.), but I'm less sure about the others. We don't really know for sure if they will perish with creation, or if they could really destroy creation at all. I think the main point in destroying creation is to force The One to admit he was wrong. The One may very well intervene to stop them, but it has been said that the corruption was too great for him to be able to rid creation of it without destroying everything himself. I think that Agares really wants The One to destroy creation, just as he hmself destroyed Nyx, to prove that The One is no better than he is. In general, agares and his followers just want to hurt those they hate as much as they possibly can. In this they become very shortsighted (since Mammon isn't doing his original job) and do not act in their own long term best interest. They may know they are helping to destroy creation and thence themselves, but they do not care about that nearly as much as making sure others don't win.