Under King Adrian's rule, the Eagles were a small gang that were only involved in petty thievery and some smuggling. However, after his death, the gang grew into power, eventually taking control of half of Northcliff. The gang was responsible for the annihilation of The Knight Order around the time of King Adrian's death. The gang gave the Knights anonymous tips about illegal deals going on at night, and once the Knights left they attacked their outpost, with organized professional archers, and wiped out the whole order, excluding Jace, in one night.
It's said that they recruit the worst kind of people, murderers, thieves, bullies and the like. The gang consists of skilled archers, who are renowned for their "headshots." Their skill is demonstrated in Chapter 1 in Davenside, where the Eagles kill Aida's entire camp, aside from Aida and Sky, without even giving them a chance to fight back.