Precious minerals make the modern world go 'round—they're used in everything from circuit boards to tableware. They're also some of the most toxic materials known to science, and excavating them has proved so dangerous over the years, some have been phased out of industrial production altogether. 

While dinosaurs get all the attention, discover why prehistoric creatures like the terror bird and the Titanoboa are just as terrifying.

For about 135 million years, dinosaurs were the undisputed rulers of the Earth. And they might still have been today if not for the cataclysmic comet that struck Earth some 65 million years ago. However, our planet has been around for a lot longer than the dinosaurs’ reign and, as it turns out, nature has been quite adept at producing nightmare-inducing monsters other than dinosaurs.

On land during the day, we humans rule. Or at least we're considered top predators, and with our feet on the ground, we're in our element. In the sea, sans a boat, forget about it. We're too slow, too encumbered with gear, and often too stupid to be much more than prey. What's to worry about down there? Plenty!

Yes, this list is subjective, but it's based on research aimed at finding the creatures of the deep that conjure the most compelling combination of frightening personas, actual aggression and/or real pain or death to humans. More often than not, pain and death from sea creatures is avoidable, especially in the case of two on this list that inflict most of their damage in home aquariums and restaurants.