Nazguls are golems that used to be people, and can take a lot of punishment.
Nazguls are distinguished by their appearance. They wear black Jedi robes with either a black head or a Darth Maul head turned backwards so the face is concealed by the black hood they wear along with a black cape. They carry Magic Silver Knives Of Doom and Dismemberment(tm) with which they snuff the lives of hardend Brickwars soldiers with relative ease.
They will await orders from the highest ranking officer in your army. Once given a target, they will pursue the target until either they or the target is dead.
The only exception to the above rule is if the bearer of the One Ring appears on the field. Then, one of two things will happen. Either (a) the bearer is Sauron, and the Nazguls obey his every command, or (b) the Nazguls will flock to the Bearer and attempt to kill it. If one of the Nazguls retrieves the One Ring, then it will vanish from the battle, to return the Ring to Sauron. At that point, any remaining Nazguls will return to their CO for new orders.