Warden Lore Theory.

*Title: Warden Lore Theory - The Warden was built to fight the Wither* My theory about the Ancient Cities: The underground civilization was at war with the Wither civilization for centuries. One day they had an idea: To create a creature as strong as the Wither to protect them - The Warden. They failed to give him eyes, so they made his hearing 1000x stronger instead, perfect to hunt the loud, flying Wither. But when the great war came, the Warden couldn't tell friend from foe. He heard everything and everyone, and killed them all. That's why he's called "Warden". First he was supposed to be the Warden of his people. Now he is the Warden of a dead prison - the Ancient City - guarding ruins of a war that ended 1000 years ago, without knowing it's over. It explains why Ancient Cities have wool on the ground and why the Warden always comes when he hears you. He is still doing his job.