Buta No Shiro (5E)

From publisher blurb:

For 4 Level 10 PCs

A warthog-headed rakshasa, Achellios the Glutton, has gained influence over a town’s magistrate. The creature uses its powers to uncover illegal activity and read wrongdoers’ minds, then with its message ability it whispers the details to the magistrate while he’s alone—resulting in a remarkably crime-free town. When the PCs enter the picture, either traveling through the area or perhaps returning to their once-quiet hometown. Achellios recognizes the threat the adventurers pose and immediately starts turning the magistrate against them with every scrap of information it can think of.