Answer:
My voice is tender, my waist is slender and I'm often invited to play. Yet wherever I go, I must take my bow or else I have nothing to say.
Scythe of darkness, Shadow’s light. Guiding eye of thirteenth sight.
Iron roof, glass walls, burns and burns and never falls.
Voiceless it cries, wingless flutters, toothless bites, mouthless mutters.
The itsy bitsy teeny weeny yellow polka dot variety is quite popular.
What is always coming but never arrives?