" Well, good-bye for now," he said, rolling his neck as if we hadn't been talking about anything important at all. He bowed at the waist, those wings vanishing entirely, and had begun to fade into the nearest shadow when he went rigid.
His eyes locked on mine, wide and wild, and his nostrils flared. Shock - pure shock flashed across his features at whatever he saw on my face, and he stumbled back a step. Actually stumbled.
"What is -" I began.
He disappeared - simply disappeared, not a shadow in sight - into the crisp air. "

― Sarah J. Maas , A Court of Thorns and Roses (A Court of Thorns and Roses, #1)