He can tell that Emet-Selch is enjoying this. Good. If he's enjoying what Hythlodaeus is doing, he's not casting glances at others. He kisses him again, before smiling- it's more like his old self this time, less unpleasant, but it's still a touch dangerous.

"Good. We don't want to make me angry, now do we?"

Or perhaps Hades does want to make him angry, but that might not end well for anyone involved. The last thing Hythlodaeus needs is a punishment for attempting to vaporise someone because Emet-Selch looked at them for too long.