Sky Pirates were outlaws who attacked the Leagues' sky ships, intercepted their cargo, and undercut their prices to make a living. Despite the illegal nature of their trade, many Sky Pirates were noble and valiant, though an unscrupulous few were involved in the slave trade. They were the only ones who prevented the Leagues from total monopoly of all trade throughout the Edge.
Role in the Quint and Twig trilogies
During Quint and Twig's time, Sky Pirates were involved in complex interactions with the Leagues. Though the Leagues despised the Sky Pirates, they tolerated them because they were useful weapons for internal competition. Although every League was intent on gaining more power than the other Leagues, no Leaguesmaster dared to directly order an attack on another League. Instead, they hired Sky Pirates to raid rival League ships for them, enabling the Leagues to create a pretense of unity and cooperation.
Nevertheless, occasionally, the Leagues would try to defeat the Sky Pirates utterly, driven by their desire to control the skies. Notable instances were the Battle of the Great Sky Whale and Ruptus Pentephraxis's massive attack during Clash of the Sky Galleons. However, the Sky Pirates always had nimbler sky ships, and beat the Leagues every time they tried this.
Role in the Rook Trilogy
In the Rook trilogy, Sky Piracy had ended along with the First Age of Flight, but many former Sky Pirates continued their activities in other ways. A group of Sky Pirates headquartered in the Armada launched attacks on the Shrykes along The Great Mire Road. Later, these same Sky Pirates assisted the Undertowners in the Third Great Migration.
During the Quint and Twig trilogies, Sky Pirates roamed between Undertown and the Deepwoods on their sky ships during the course of their work. Sky Pirate captains often assumed special names, usually a word relating to the weather, followed by the name of some kind of creature.