There's no 'mystery' (to/as to/about) why we're here. = It's no 'mystery' why we're here. [=we know why we are here]
His success is something of a 'mystery'. = His success is a bit of a 'mystery'.
We'll reveal the identity of today's 'mystery' guest after these commercials.
(..) ...if only for a short while. King me. -Chess. Now there's a game of kings. -What? Civilized. Strategic. And a total fucking mystery. I hate it. Let me teach you someday. Sure. We could get a board together. You're talking to the right man. (..)1994 The Shawshank Redemption