Answer:
I move without wings, Between silken string, I leave as you find, My substance behind.
Die without me, never thank me. Walk right through me, never feel me. Always watching, never speaking. Always lurking, never seen.
A circle of stones, never in rows. Stacked one on the other, mystery it sows. What is it?
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
Turns us on our backs, and open up our stomachs. You will be the wisest of men though at start a lummox.
If itβs information you seek, come and see me. If itβs pairs of letters you need, I have consecutively three. What am I?