"Mister Death" was the mocking name given to an adder by Brookflow. She and Sister Armel encountered the snake in the ditch in Mossflower Woods and he introduced himself simply by stating "I am death to all beastssssss!"
Brooky was unimpressed, believing him to be only a harmless grass snake. She knocked him out by whacking him on the head four times with her and Armel's ration packs. Armel was quite impressed, sure that the adder was going to kill Brooky. Brooky stated that she knew she was all right because the snake didn't have a diamond pattern along its back. She then wiped off the unconscious snake's back to show her, only to discover that it did have such markings and was indeed an adder. The two left the snake to lie in the ditch, noting that it would have a headache that would last until midsummer. "Mister Death" was never seen again.
He is the one of the few snakes not to die, and one of the very few characters in the Redwall series not to be given an official name.
He is also the only villain to not die at the end of Rakkety Tam.