They live in soil and walls and swallow their prey whole. Their outer skin is tougher than it looks, and they are highly resistant to magic. From the inside, they are fragile. They have no eyes and search for prey by smell and vibration. In this case, it was attracted by the smell of mother's milk. They nourish their prey by swallowing them whole and dissolving them in their digestive juices. In this case, Stille is not digested due to the "Blessing of BE", but since it can also take nourishment from the body fluids, it is useful to the worm as a snack and will never be released.