"If all I wanted was a soul, I'd have taken it at your nest." You see this shade? This is an incredibly smug shade. This is the best solution that could have come out of this, as far as he's concerned - he didn't break his word, he got to irritate the harpy, and still got his revenge. The man who took any job, uncaring of who he harmed in pursuit of it, is now being killed by a group of hunters, uncaring of who they harm in pursuit of monsters.

It's a twisted representation of circumstances that's probably only satisfying to a shade.

"I suggest you move before they start looking for the other monster. Or realize they haven't slain who they thought they did," the shade offers, just as innocently. Then he turns and starts drifting away.