The Complete Book Of The World: Rongo Rongo was a book-type Teigu. It was wielded by the Empire's Saikyuu and was later used by Akame. Akame lost it when a storm destroyed her ship.
The book contained every single map in the world. The information about the Empire's territories was especially detailed and included every detail about the mountains and lands. On the last page, there was a prediction of natural disasters that will happen in the future.
It also contains all information regarding every world, and Akame studied Wakoku's language before she traveled to the Wakoku.