Vampire squid is an apt name for a creature that lurks in the lightless depths of the ocean. Comfortable at 10,000 feet (3,000 meters) below the surface, these diminutive cephalopods navigate the blackness with eyes that are proportionately the largest of any animal on Earth. The species gets its name from its dark, webbed arms, which it can draw over itself like a cloak.
The Pacific viperfish has jagged, needlelike teeth so outsized it can't close its mouth. These deep-sea demons reach only about 8 inches (25 centimeters) long. They troll the depths up to 13,000 feet (4,400 meters) below, luring prey with bioluminescent photophores on their bellies.
The nightmarish fangtooth is among the deepest-living fish ever discovered. The fish's normal habitat ranges as high as about 6,500 feet (2,000 meters), but it has been found swimming at icy, crushing depths near 16,500 feet (5,000 meters). Fangtooth fish reach only about six inches (16 centimeters) long, but their namesake teeth are the largest, proportionate to body size, of any fish.