This is a monster idea that popped into my head the other day.
The creature is likely some sort of faerie or undead. It is tall and lanky with some disfigurement to the face (I see a face without eyes and a mouth full of sharp, needlelike teeth similar to the monster in Pan's Labyrinth). The creature is preternaturally fast and strong, possessed of more grace and strength than one would expect given the gangly, slim frame. One it gets ahold of you, the creature grips a limb or your face very tightly, running its thumb or fingertips into your flesh (no actual penetration). Beneath, hidden away from sight, impressions begin to form on your very bones. The rubbing causes the bone to edge out of the way like hard clay being worked. Eventually, the creature can rub through the bone (effectively breaking it) and they collect bones and skulls to adorn their homes, each formed into something it's not.
Edit: Right after posting the above, I shared the idea in the OYT chat room and received these ideas:
#contraserrene:: Eldric, I like that idea. Creepy without being actively gory.
#Baquies:: Sounds like something from world of darkness
#contraserrene:: I imagine them, especially if they're the less nice kind of fey, deciding that they LIKE you.
#contraserrene:: So they give you a present.
#contraserrene:: Made from you.#contraserrene:: "Here, a mask to cover that all-too-human face! Its features are delicate, sharp, like our own!"
#contraserrene:: "We made it from your left hand! So you'll need to use your right to hold the mask to your face!"
#Baquies:: never enough evil fey in my opinion
Eldric IV:: My pooka was Unseelie. Does that count?
#contraserrene:: "Whoops, the mask is a little too narrow to conceal your whole face. Your cheekbones are too wide."
#contraserrene:: "Luckily, we can remove them."
DerekDyer:: Candles are the best during a scary movie
#Baquies:: YOu could make teh creature like the tooth fairy's older brother, he takes a femur and leaves you a few copper
#contraserrene:: The Marrow Fairy.
DerekDyer:: cause they make things dance on the walls all around
Eldric IV:: Feymur?
#Baquies:: I ran castle raveloft during a power outage, that was kinda fun
#contraserrene:: Looking for a word implying "delicate touch."
Eldric IV:: Caress? Stroke?
#contraserrene:: That could be the name of one of these fey.
Eldric IV:: Funnyhone.
#contraserrene:: The species might be called... exquisitists. Or that could be their name for their artistic practicioners.
#Baquies:: They start with the small bones and visit you every few nights to take anotehr, first the tip of a toe or finger, then a knee cap. and so on. the party must set a trap
Eldric IV:: Straight fingers, arms, and legs are just too boring. You must look beautiful.
#contraserrene:: What better bait for the trap than a cold iron pot, propped open by a stick on a string, baited with the bones from that night's main course at dinner?
#contraserrene:: They love the Golden Ratio.
#contraserrene:: So they want your extremities to have a "more pleasing" rest state matching the spiral of a nautilus.
#Baquies:: OK, they come in at night and reforge re shape a certain bone every few days, you slowly acrue Dex and Con and skill penalties
Eldric IV:: And your own personal crown protruding from your forehead.
#Baquies:: If you go to the lair of these things, they are filled with mishapen hoards of victims and mounted skeletons of the deceased.
#contraserrene:: They can sense with a touch whether a bone has been reshaped before. They consider Cure spells that knit sprained and broken bones to be especially crude "reshaping."
#contraserrene:: Bones that have been "sullied" in such a way are considered useless.
#contraserrene:: Of low quality.
#Baquies:: Yeah, if you cure of fix theri work, they take the bone next time
#contraserrene:: Their economy, such as it is, would involve trade in bones that have never been altered by anyone before.
Eldric IV:: Bones whether or not yet emancipated from their current owner.
#contraserrene:: Of course, in a fey society, people won't respect the property rights of their peers...
#contraserrene:: Thus, there's a constant need for new captives.
Eldric IV:: I imagine children would be an easy way to store your "money."
#contraserrene:: The good news is, they let you go after a month or two.
#contraserrene:: The bad news is, they let you go after a month or two.
#contraserrene:: These boneshapers would consider animated skeletons a mockery of everything they hold dear; they would craft weapons specially designed to destroy skeletons, liches, etc.
#contraserrene:: They consider bone golems to be a lesser affront, but still an affront.
Eldric IV:: They can themselves wade through a skeleton with their bare hands.
#contraserrene:: Osseries, on the other hand, are a grand thing.
#contraserrene:: "Look, these shortlived people have set out a market for us."
#contraserrene:: They steal the bones from an ossory- the ones that were never magically healed, that is- and leave behind payment.
#contraserrene:: If you're lucky, the fairies that stole your ancestors' bones left you some gold, gems or magic.
#contraserrene:: Unfortunately they don't prize such things so much. They'll leave you something more personal.
#contraserrene:: Never, ever, ever express a wish in their presence that they could "grant" for you.
#contraserrene:: "But you said you wished you could fly! Now you have wings. Sort of. You can flap them and make a wind, so it feels a little like flying. The constant agony is just a sign that you're still alive; you should welcome it!"
Eldric IV:: I suppose one or more of them could go a bit "unusual" in the head and start grafting other bones onto/into people.
#contraserrene:: They might see that the way the Amish see teenaged wandering.
#contraserrene:: A phase everyone goes through before settling down to a more "mature" lifestyle as a bone-alterer.
#Baquies:: It starts with collecting old teeth and just goes bad from there
DerekDyer:: not bad