I've had a look at some of the uniques available here and noticed that Tyrael's Might has a property called "Slain Monsters Rest in Peace". What is this?
Nature's Peace is a ring with that effect.
Nature's Peace: "Slain Monsters Rest in Peace" means that the bodies can't be resurrected or they can't be used to raise skeletons (Necromancer). They can't be used for Corpse Explosion either. It will work only if you kill the enemy with a physical damage or elemental (Blizzard or Fireball) and not magical damage. The ring will work for the Paladin's Blessed Hammer skill.
Slain monsters Rest In Peace effectively stops skills like corpse explosion, find item/potion, redemption, etc from working on the would be corpse. This is specifically useful for hardcore players farming keys from Nihlathak, it basically makes him an easy target with not much killing power.