The Abyssal Region is absent of solar light, has high pressures and is separated from surface food supply. Because there is little sun light, bioluminescence does occur. The abyssal region covers over 85% of all ocean basins. It's a large and vast, relatively flat plain. It's covered in thick sediment that's moved by turbidity currents that can go as fast as 50mph. Sometimes these turbidity currents agitate sediment near canyons causing the sediment to slide down to the abyssal plain creating a river like bed as they go. Some sediment is marked with trails of an organism like a brittle star.
Brittle star ( left )
Brittle star ( left )