Blind Crab

They have six, long and thin legs. At young ages their shells are colorless, and you can see into them as you would look through crystal. They are related to reavers, and are located mostly in the underworld.

Known varieties include:

Lantern Crab: A miniature species who can fit entirely on a babies thumbnail. They're bodies are luminous.
Behemouth Crab: Large crabs located in Delving's Deep.