Answer:
What an fill a room but takes up no space?
By the way, what never moves, wears shoes, sandals and boots, but has no feet?
What always runs but never walks, often murmurs, never talks, has a bed but never sleeps, has a mouth but never eats?
A man calls his dog from the opposite side of the river. The dog crosses the river without getting wet, and without using a bridge or boat. How?
Held firmly in the hands, like a sword it cuts deep. Bloodless strokes, all, then forward we leap.
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.