Sometimes simply called “Living skeletons,” bone-dancers are far more dangerous than that simple name would imply. They are aggressive, cunning, lethally accurate with their blades, and very hard to kill. Their only weakness is a lack of numbers.
The dancer itself is a small wisp, a mote of light about the size of a woman’s fist (sometimes as small as a walnut). It orbits the bones it has claimed in a complex pattern that differs between each individual, and appears to be reflective of mood. It dances faster during combat, and slower when at rest.
What makes the dancer so dangerous, of course, is their ability to animate bones and construct a roughly human-shaped puppet to do their bidding. The puppet is literally nothing but bones; there are no muscles, tendons, or anything holding it together but the power of the dancer. While this does mean that destroying the dancer destroys the puppet, it also means that the puppet is largely immune to conventional attacks. Even destroying the bones is little more than a stopgap; the dancer can still animate the shattered splinters, though it does appear to prefer whole bones.
The only thing that can prevent a dancer from animating bones is fire—but extremely hot fire, enough to reduce the bones to ash. Only a very powerful forge can produce enough heat to accomplish this, so this remains an unviable technique in combat.
Therefore, every hunter insists the only way to destroy a bone-dancer is to destroy the dancer, and to focus on it to the exclusion of all else. They tell stories of the more intelligent bone-dancers abandoning humanoid shapes in favor of formless clouds of whirling bone when pressed; if one tries to block every individual bone among the storm, they will simply be overwhelmed.
However, attacking the dancer is more difficult than it sounds. Not only is it small and fast, but it is intelligent (at least at the level of a cat, and likely far smarter), and will quickly learn to use its bones to shield itself from dangerous strikes. Small nets have had some success in capturing the creatures, but this is not recommended, as it is difficult and dangerous.
There are two strategies that work best against bone-dancers. The first, and simplest, is to simply crush the entire puppet under a large rock and hope that kills the dancer. This is both easier and harder than it sounds: On the one hand, bone-dancers live exclusively in rocky terrain, so it is rarely difficult to find an appropriately-sized boulder. On the other, bone-dancers are clever, so this trick will only work if you catch them by surprise. And they appear to see in all directions at once, so this is harder than it sounds.
The other option is to use cold. Dancers do not react well to freezing temperatures; if it is cold enough that there is still snow on the ground, they will move significantly slower. Throwing them in a freezing lake appears to kill them outright. Of course, bone-dancers are intelligent enough to stay hidden during the winter months, and especially avoid freezing lakes, so Professor Haber’s “freezing flask” might work best. Try not to miss.
Failing either or both of the above options for whatever reason, the only option left (assuming running is not available) is to fight it using more traditional means. Sniping it from a distance is difficult, but possible, but in melee combat a shield is very strongly recommended. Then, it is simply a matter of watching the pattern, waiting until the right moment, and striking when the dancer is unguarded.
Bone-dancer bones have a few minor uses in potions, but are generally agreed not to be worth the trouble. The corpse of the dancer itself, however, is extremely valuable, and should always be collected if at all possible.