Answer:
What's as small as a mouse but guards a house like a lion?
Steals an event or even a mood. Reveals the truth or shatters it.
Stealthy as a shadow in the dead of night, cunning but affectionate if given a bite. Never owned but often loved. At my sport considered cruel, but that's because you never know me at all.
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
The root tops the trunk on this backward thing, that grows in the winter and dies in the spring.
Before Google, we actually had to physically look things up in this building full of knowledge.