Pathfinder 1e Villain of the Week #5: The Ghost of Jacques du Redmond
He haunts his own rural manor, much like a 19th century plantation house.
A translucent figure dressed in noble garb of several centuries past.
His ghost touch conductive dagger means he can strike at PCs even when incorporeal, for full damage, sneak attack, and channel his corrupting touch through the strike.
He can flit in and out of walls and floors, always fighting on his own terms, unless the party finds a way to render him vulnerable. Combined with his rogue abilities, this makes him a truly terrifying foe, especially since by giving up part of his sneak attack damage, he can demoralize a foe, which then makes them vulnerable to Shadows of Fear, allowing him to sneak attack them as if he were actually flanking, even though he is alone.
He's technically CR 8, but just adding a few haunts and special effects to his house and playing him intelligently can make a much higher challenge.