Oh, he was trying to flex on her. Hammerhead remains resolute, nothing in her eyes changing when Murmur's strength clashes against hers or the chill comes on. This is just evidence that he has a superpower or magical ability, and that's nothing unusual.

"Yes I want to know with certainty, shit-for-brains," she snarls. "Fucking keep up!"

Having powers didn't mean anything. The Head could replicate that stuff somehow.