Their capitol of Constantinople was famous for having deflected many invasions, and the Byzantines get tougher buildings. The Byzantines had a head start over their neighbors and arguably reached their zenith while the rest of Europe was in the Dark Age, and pay less to advance to the Imperial Age. Their unique technology is Logistica, referring to the Byzantines' strong military tactics and grants their Cataphracts trample damage to attack multiple enemies at once. The Cataphract is one of the few true counter units to infantry, slightly weaker than Knights. The Byzantines referred to themselves as Romans and retain many characteristics of the classical Roman Empire, such as their unique unit, the Cataphract, a type of heavy cavalry that happened to be present in Age of Empires I.
The Byzantine Empire are an Eastern European civilization especially active in Western Asia, and are also known as the East Roman Empire.
The Aztecs did not have horses or gunpowder, and the Age of Empires II Aztecs are no different. They were famous for their bloody and ardent faith, with their relics generating extra gold and their Monks receiving extra HP per Monastery technology researched, allowing their Monks to join other soldiers on the battlefield. Being a highly military civilization, the Aztecs also have a general creation bonus across the board for all their units. The Aztecs were also known as a hard working and innovative civilization, and their villagers' carry more resources and get the Loom technology free. Their unique technology, Garland Wars, references the "flower wars" which the Aztecs organized amongst their allies in order to provide more sacrifices. The Jaguar Warrior is thus a heavy infantry unit who is strong against other infantry units. Their unique unit is the Jaguar Warrior, the highest rank of warrior in the Aztec army, wielding a wooden club studded with obsidian shards sharp enough to decapitate men and horses. The Aztecs are a Mesoamerican civilization appearing in The Conquerors Expansion.