What do you use to stop someone from advancing?

Above your brows I boldly spread, A patch of calm before what’s said. I wrinkle when you think or dread, And shine when overheated.

A beautiful end to an ugly start, or at least that's how the tale goes. But dive in without water, and I'm a beautiful start to an ugly end. Oddly, I don't really do the action that was named after me.

With a pole up my backside. I feel no pain. That might change If I only had a brain.

I'm sometimes holy But never wholly made of Hass.