The term 'Mulan Invaders' refers to the Huns, a nomadic people who lived in Central Asia during the 4th century. They were known for their military prowess and were often hired by other empires to fight in their wars. The Huns were eventually defeated by the Chinese in the 6th century, but their legacy lives on in the 1998 Disney movie Mulan, which tells the story of a young Chinese woman who disguises herself as a man to join the army and fight against the invading Huns.