"A rough gang of Achaieriders"
They are a band of thieving marauders, male and female, that ride giant flightless birds called Achaierai. The group is made up of Achaierai Riders and Achaierai Drummers/Dancers. Some look like they could be Hobgoblins. Their weapons include mainly hand axes, crossbows, scimitars, and chains. The Flock are opportunists who take advantage of a less stringent rule of law.
They wear distinctive leathers, boots, a helm with goggles and a face shield. They ride a top Achaierai in a saddle holding big long handlebars. On the Leather Jackets is a symbol in some paint - a billowing black cloud.
The second time they were encountered was in Episode 27: Feathers and Fangs.