In legend, the ankou is a personification of death from Breton and Cornish folklore, a kind of dark psychopomp. But the ankou in the Pathfinder game is a much more decidedly fey and murderous creature (courtesy of Pathfinder #36: Sound of a Thousand Screams). Its party trick is creating up to four shadowy duplicates to fight alongside it. As instruments of their fey lords’ dark wills, ankous terrify other fey—no wonder, since their claws function as cold iron weapons—and nasty spell-like abilities like prismatic spray and circle of death only add to the body count.
All those special abilities mean the Bestiary 4 entry doesn't have the room for all the juicy flavor tidbits from the original: “an ankou slumbers in a cocoon of darkness”...“the only words they can utter are those whispered telepathically into the victim’s ear an instant before death, and those words are spoken in the voice of the one who sent the killer”…“one of these assassins might be told to kill the victim many times over—murdering its target, waiting for its connection to the First World to reform it, and then killing it again.” [For the unfamiliar, this last bit is a reference to the regenerative powers of Golarion’s fey realm.]
One final note is that each ankou serves a different fey lord. So there’s no reason that every ankou has to look just like the winged skeletal shadow-horror in the books. I imagine the progenitor of the quickling race might fashion his ankou to look like a knife-covered cutpurse, rail-thin despite its Large size. A fey lord of harvest might have a pumpkin-like monstrosity, while a spirit of the crossroads might employ a crow-monster or a hanged man with wings made of iron and rotted ropes. Then again, winged skeletal shadow-horrors that nest in cocoons of darkness do have a certain primal appeal, and might be symbols of terror throughout the fey realms no matter who they serve.
While exploring an undocumented cavern, adventurers come upon a slumbering ankou. It attacks them upon waking and pursues them through the dungeon as best it can. If the party escapes the cavern complex it leaves them be, unless it hears them singing or they grievously wound it (reduce it to 25% of its hit points), in which case it retreats to plot its revenge—which it will enact no matter how far they go. If the adventurers kill the ankou, they are not out of the woods, for the shadow-beast’s death, however, temporary, draws the eyes of its fey master upon them.
Duke Summer’s wrath is all the more terrible for its rarity, descending almost without warning like a summer storm. On a mission to save the world, a faerie agent and her mortal adventuring allies are taking a shortcut through Summer’s realm when they break one of his strictures. Insensible to reason in the face of this flouting of his authority, he sends an ankou after the party, declaring, “And as I am Summer, the world may burn.”
Other creatures fear cold iron claws, including demons and night hags. A faerie lord allies with adventurers to take down their mutual enemy, a particularly powerful and troublesome night hag. Careful listeners will note that he promises them the obedient services of the beast “until the night hag has well and truly perished”…with not a word about what comes after.
—Pathfinder #36 80–81 & Pathfinder Bestiary 4 10
Work and life has me a bit slow to reply to reader comments (and I simply can't give everyone the props they deserve) but I do appreciate all of you who are weighing in despite these comparatively new/unfamiliar monsters.
Just a heads-up: With July 4th almost here, I’m going to be taking a vacation to do some traveling. I’m debating posting next week and almost definitely will not be posting the week after. So if you don’t see your daily entry during the next fortnight, that’s what’s up.