The same way they’re able to take human shape and move instead of sitting in a pile…
Shit, some of them talk
Free me from this flesh, brother
A dungeon suddenly becomes the corridors of the Nostromo. No matter where you hide, the skeletons can sense your BONES!
You know how their jumble of bones pulls together when you get close? Their bones wanna do that with your bones, and the osteonetic attraction that pulls their bones together let’s them know where your bones are, too.
So all you would have to do to avoid this fate would be to pull out your own bones from your body, interesting…
So the ultimate counter to skeletons are octopuses.
Nails, hooves, and rhino horn are all made of keratin; antlers are a little more complicated: https://www.amnh.org/explore/news-blogs/news-posts/horns-and-antlers-what-s-the-difference