The horrible and hated Nail Worm

Full Description
The Nail Worm has no visible eyes, but seems to have other good-working senses. It is about 20 yards long, its body covered with short hair or fur. All grey in color, it is hard to note if not moving. But if it moves, it moves fast and effectively with a sidewards wawe-like movement a few snakes are known to move. Its 'head' is not separated from the body, and has no discernible senses. The mouth seems to have many small teeth, or perhaps tentacles. The 'tail' is thinner than the rest of the body, and very hard, able to deal strong punches. The beast is maneuvreable and cunning at defeating humanoids.

The Nail Worm meets its prey in underground locations, and somehow produces a thick black cloud. In the ensuing chaos it chooses a victim, and attacks. It should be noted that all attacks deal only subdual damage, be it hitting with the tail, or constricting the victims neck, like some great snakes do. When the victim is knocked out, it begins to feed...

Nobody knows what the Nail Worm normally feeds on, and how does it survive. But the treatment of its victims is know: it begins to suck on their fingers and toes, its saliva dissolving nails.

When the victim returns to senses, the Worm is long gone, and the fingernails too. The victim is free to go and curse that $#%*@ Nail Worm!