Which of the listed empires were named the so-called “Gunpowder Empires”?

Player #25874027, one of the definitions of Book is "a major division of a large document' An example being "The Book if Genesis" as part of The Bible. I have a two volume work that contains multiple books. Each of which is a complete story of a single person's life, where each person is a reincarnation of a single soul cursed to be tormented in life until one of his incarnations redeems his sin.

Book 5 of his three volume work ?