Growing to sizes comparable to a small snake, it is not one of the most aggressive beasts on the planet. The Ko'zal worm is notable for its ability to produce a very strong type of Ko'zal silk when cocooning itself. Once the worm emerges as a moth and leaves the cocoon, Protoss workers would harvest the silk for clothing.
After the Zerg invaded, they assimilated the worm's genetic structure and the formula to create the substance. The silk protein was then added to egg and cocoon formation to enhance protection from most types of assault such as small arms fire.