'Threshing Day' answers questions 'Fourth Wing' fans have about Rebecca Yarros' series. Here's what you might've missed.

Source: Business Insider

"Threshing Day" is the latest book in the "Fourth Wing" universe. Casey Paul/MLB Photos via Getty Images/Red TowerRebecca Yarros released "Threshing Day" on Tuesday. The book unveils new lore about dragons and their riders from the "Empyrean" series.