Answer:
What's as small as a mouse but guards a house like a lion?
I'm white, I'm round, but not always around. Sometimes you see me, sometimes you don't.
What is that which, though black itself, enlightens the world without burning?
Golden treasure I contain, Guarded by hundreds and thousands. Stored in a labyrinth where no man walks, Yet men come often to seize my gold. By smoke I am overcome and robbed, then left to build my treasure anew
A box without hinges, lock or key, yet golden treasure lies within.
I am your mother's brother's only brother in law. Who am I?