The Executioner is a unique monster, found in UnNetHack at the lowest level of Sheol. He attacks fast, and his weapon of choice is the artifact double-headed battle-axe Cleaver. He is assisted in this aim by monsters such as blue slime that will freeze you in ice. He presides over a hoard including the crystal pick. If given the freedom to strike, he is quite capable of eliminating an ascension-equipped adventurer in a couple of rounds.
Be sure to defeat the monsters of the outer part of the level before melting the ice wall and setting the Executioner free! One weakness of the Executioner is that he does not have sleep resistance. A player was able to successfully anesthetise and then despatch him by means of the sleep spell and a high quality dagger. This led to the suggested t-shirt message "I knocked off the Executioner and all I got was this lousy crystal pick".
Bad move there, Dudley.
Executioners like to immediately execute adventurers who get trapped in their icy lairs. Challenging them in direct hand-to-hand combat would be headlessly stupid.
'Executioners execute!' [ Adeon ]