Zipfly
This little spirit resembles a metallic horsefly just under an inch long. While the zipfly appears harmless, its mode of reproduction is dangerous in the extreme.
The zipfly seeks out unattended surfaces and implants them with little metal teeth resembling a zipper. This zipper can be built on almost anything - wood, stone, metal, porcelain, even flesh, although the zipfly prefers smooth surfaces to rough ones. The length of the zipper only depends on the commitment of the zipfly. Most are mere inches long, but in secluded places winding zippers over a mile long have been discovered.
The zipfly completes its work by undergoing a metamorphosis, and installing itself as a non-descript metallic tab at the zipper’s end. If you encounter a zipper you think may be left by a zipfly DO NOT OPEN IT. Not only will this leave a deep and permanent pocket in the zippered object, it will also release a new brood of zipflies. If the zipper is on a person’s body, opening it can be fatal.
Once implanted a zipfly zipper is almost impossible to remove. But as long as you don’t pull the tab, it remains merely ornamental.
