Answer:
What goes further the slower it goes?
Walk on the living, they don't even mumble. Walk on the dead, they mutter and grumble.
This is in a realm of true and in a realm false, but you experience me as you turn and toss.
I am round as a bowl, deep as a tub, but all the world's water couldn't fill me up.
Glittering points that downward thrust. Sparkling spears that never rust.
People take me on walks and I run and have fun. What am I?