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.
(..) So what do you propose? What you got? I warned you. How did you do the That far exceeds your mind?. If you want to happen but you have to me solve a mystery. And what happens if we go ahead? Do you listen to my riddle? What is probably harder A pound of goose feathers or a pound of gold? (..)2011 The Dragon Warrior