Satan had a razor blade smile. One that cut right into the heart and straight through to the soul. Satan smiled a lot throughout the day. A hundred different wounds on a hundred different souls. Some would heal. Most didn't.
His smile was completely wasted on Wrath. The Sin was less a slave and more a favored pet without a leash. He came when he was called. That was all that mattered.
"Have a marshmellow, Cain." Using the mortal alias made Satan chuckle. Why would be anyone's guess. Another inside joke with God? More then likely.