Silver Demon Skeleton

It says that the demons killed by the sword made of pure silver are doomed for eternity, but powerful wizards using black magic can enter the realm of the death and use those souls to reanimate skeletons, which bones turn to silver, and makes them very powerful enemies. While they have bones for the armor, it can be seen behind the bones the evil black body which represent the fallen demon covered with glowing red essence. Their heart is the only weak spot, and Silver Demon Skeleton can be only killed by the silver sword blessed in the altar of Heavens. One pierce through the heart and skeleton will shatter and making demon disappear into abyss.