Judge Death... Dark Judge... with a Lisp, the son of a homicial dentist, and a undead genocidal monster from an alternate dimension, where Life itself became a crime....
Death is capable of possessing others bodies (which then mutate into his hideous ghoul form. Kind of a Grim Reaper with an attitude for maximised efficencey.
His fellow judges, are Judge Mortis, Judge Fear and Judge Fire. There are also two 'Sisters of Death' powerful magic weilding undead hags. Dark Judge incursions usually result in massive casualites, as their spirits leave their bodys when badly damaged, and simply possess another. Incendary Rounds seem to be the most effective weapon (except Judge Fire - where obviously water is the key)
Usually its Psi Divisions job to deal with them, with the other Judges containing them. Casualites usually are in the thousands (though Necropolis - when the Dark Judges took control of MC-1 resulted in millions - when coupled with the Zombie War with Sabbat, MC-1 lost 50% of its population).
Death has turned up a number of times, and more often is the nemesis of Judge Anderson, rather just Dredd (Andersons first appearance was in the First Judge Death Story - In which she captured his spirit in herself and encased her body in Boing (the miracle ricochet plastic).