What makes the Black Sea Devil a deep sea mystery is there is less known information about it than the giant squid.
What we DO know is this:
A Female black sea devil can grow to be about the size of a baseball. The males are even smaller and are actually more of a parasite than a fish. In order to survive, the males must bite on to the female. Their tissues will fuse together, and the male provides sperm while the female sustains the male.
Black sea devils have a gaping mouth, needle-sharp teeth, a slightly startled expression, and a lure atop their head that lights up. It’s unknown if there is a pattern for the illumination or if the light is continuously kept on. This lure is used to attract prey.