Mr Big is the codename given to Lester Smalls, a diminutive man in a giant suit.
A slow, stupid creature that crawls onto people and latches onto them, often on feet, hands, and other extremities, numbing down the area and slowly feeding on it. It's easy to avoid while awake, but nearly impossible to remove once attached. Many an adventurer has been forced to hack off an arm or leg after waking with a Stoneleech wrapped around it. Sleep with one eye open! (This idea came from "Wizard's Rule")