He reached and grabbed Potter’s left arsecheek, kneaded it, enjoying Potter’s slight flinching and tensing, then pulled it to the side, and landed the first strike on the unharmed left side of the sensitive crack. Potter’s entire body tensed, his magic surged like tides called by the moon and his back arched like a feline ready to attack, he tried to stay silent, but as he let out a breath, the first trembling moan broke out of him.