Walking Dead and Zombies are the level 2 creatures of Necropolis. They are recruited from the Graveyard, and can also be raised with Basic Necromancy if the hero has equipped the Cloak of the Undead King.
"Walking Dead and Zombies are magically animated corpses. Zombies have a 20% chance to cause disease in creatures they attack. Diseased creatures have their attack and defense ratings reduced by two for a period of three rounds." RoE manual
Disease special ability
Zombie attack has a 20% chance of causing the living target to become ill, thus having their attack and defense values reduced by two for a period of three rounds. The effect occurs before the target stack has a chance to retaliate. Disease can only be removed with Cure spell. Since it counts as a level 2 effect, it does not affect any creatures immune to level 2 spells, and can be prevented by Power of the Dragon Father and Cape of Silence 
artifacts, or Cursed Ground magical terrain. Orb of Inhibition and Anti-Magic Garrisons are not hindering this ability, though.
Heroes with a specialty
Straker the Death Knight has walking dead as a specialty, which increases the Attack and Defense skills of any Walking Dead or Zombies for each level attained after 2nd level and gives them a speed bonus of 1.
See also:
Skeleton
Skeleton Warrior
Walking Dead
Zombie
Wight
Wraith
Vampire
Vampire Lord
Lich
Power Lich
Black Knight
Dread Knight
Bone Dragon
Ghost Dragon
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