Riddle

I have no name, emerging from a sandy lair

Character without depth no shadow I cast

A child's game of peek-a-boo where I'm there in a silver stare  

Knocked down by a baby's blow, another round I won't last

Born orphaned from an infertile mother

In a land where right is left and what was left is right

Twin with no sister or brother

Black back, face reflected light

With no teeth or mouth old women are afraid of me

No ears your secrets I keep

Looking into another I see eternity

Always standing I never sleep