Greetings,
We are just wrapping up Burnt Offerings. The party encountered Malfeshnekor while already at low HP and resources and took a beating. Instead of a TPK, I had Malfeshnekor escape via dimension door and look for an easier meal. I want him to remain a looming threat; an evil menace that they have loosed on the countryside (and Sandpoint).
Question: What would Malfeshnekor's goals be now that he is loose? I know his immediate goal is eating. There are plenty of goblins left at Thistletop to satiate him for now. What about after that? How can I make him a threat that the PCs need to address?
You can make him subjugate one of the other goblin tribes, for example the Mosswood goblins. Barghests are considered divine creatures by goblins, and he would have no problems doing that. He could then make the goblins kidnap people from the farmlands to the south. One of the farmers could arrive to Sandpoint asking for help against these goblin raids. If the PCs don't act, Malfeshnekor could unite all of the goblin tribes and finish what Nualia started, performing a full-scale raid on Sandpoint.