The Cloak of the Undead King is a combination artifact in Heroes of Might and Magic III: The Shadow of Death. It is created by combining three Necromancy artifacts:
Besides the bonuses to Necromancy (a total of +30%) provided by the individual artifacts, the Cloak allows a hero to raise units other than skeletons from slain foes. A hero with basic Necromancy can raise walking dead/zombies, wights/wraiths with advanced, and liches/power liches at the expert level.
If the hero has zombies, wraiths, or power liches in their army, the upgraded creatures will be created. Otherwise, the artifact creates walking dead, wights, and liches.