Answer:
At night I come without being fetched. By day I am lost without being stolen.
This is in a realm of true and in a realm false, but you experience me as you turn and toss.
He has married many women but has never married.
In the evening I'm long, in the morning I'm small; When seen in a ballroom, I'm nothing at all.
It cannot be seen, it weighs nothing, but when put into a barrel, it makes it lighter.
If you can spot one of these eastern warriors, it means they're not doing their job right.