Immortals
During the growth of the Persian Empire and the Greco-Persian Wars, the 10,000 heavy infantry soldiers known as The Immortals served as both the Imperial Guard and the standing army. They were the first Persian Empire's elite force. The honor of being picked to become an Immortal was amazing. They were known as "Immortals" by Herodotus, whose works are largely responsible for the historical information we currently possess about these illustrious warriors.
They were given the moniker "Immortal" because no one in the 10,000-person force was ever killed or seriously injured before someone else took his place. Thus, from a distance, it may seem that every infantryman was 'immortal,' and their replenishment might have amounted to a resurrection of sorts.
They had advanced equipment, and their armor sparkled with gold. They were armed with wicker shields, short spears, swords or big daggers, bows, and arrows, according to Herodotus. They also wore a unique headpiece, which was maybe a Persian tiara.