In the real world (or at least what I perceive to be the real world) the Ancile was the legendary shield of the Roman god Mars, which fell from the heavens to Rome. A voice was heard from the heavens declaring that Rome would be "the Mistress of the world" so long as the shield was preserved, there by acting as a safeguard or palladium of Rome.
Numa Pompilius, successor of Romulus and second king of Rome, declared there were to be eleven other shields created, called the Ancilia. These Ancilia were to be exactly like the first down to the most minute detail, so if ever someone tried to steal the Ancile (like the Palladium was stolen by Ulysses) they would not be able to distinguish it from the fakes.
|A Roman Apex|
In order to further protect the Ancile from theft an order of priests was founded called the Salii. The Salii were the patrician youths of Rome, the sons of the elite family lines, who were trained in combat and were equipped with embroidered tunics, armor (breastplate), sword, apex (a spiked helm), and a crimson paludamentum which was a ceremonial military cloak normally reserved for Generals and officers of the army.
Each Salian priest was charged with the protection of one of the Ancilia within the temple of Mars in Rome. Each Salian guard would stand guard within the temple holding the shield he was given to protect never knowing if the shield he held was one of the eleven Ancilia or the true Ancile.