Yes that is a mystery indeed! Even though I know the final outcome "all saved", how it all will happen is a mystery.
Do a search on "mystery" on biblegateway and you will find some great verses. I always found it curious that it was called "Mystery Babylon" in Rev... I guess the ETers have thier own "mystery" too...
For me, the Babylon part is the part in us that is at emnity against God . .the carnality in us . . .and as such, it takes truth and clouds it up so that it becomes more of a mystery than a reality. Thus, the title "Mystery Babylon" As my mind traduces (definition of devil again) the Truth of the Word, it takes simple truths and complicates them . . it does the opposite of John the Baptist's message, it takes straight roads and makes them crooked, and it takes flat plains and makes mountain ranges out of them. The devil as the traditional church paints him out to be, has nothing to do with it . .it's the devil processing within me that mystifies life into darkness.
Sorry, I'll get off my soapbox now . . .