Answer:
I run up and down the stairs without moving
With a halo of water and a tongue of wood, stone as skin long I stood. What am I?
I tremble at each breath of air and yet can heaviest burdens bear.
Born in the ocean and white as snow. When I fall back to water I disappear without a trace.
What has many teeth but can't bite?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.