Sons of the Harpy

The Sons of the Harpy are a militant group from A Song of Ice and Fire and Game of Thrones, serving as the main antagonists of Daenerys' storyline in Season 5. They consist mostly of former slavers and wish to restore slavery in Mereen by removing Daenerys from rulership of the city.

Biography
A member of the Sons of the Harpy slits the throat of White Rat, an Unsullied, when the latter approaches a prostitute and pays to be embraced by her. The assassin, who was in league with the prostitute, leaves his mask at the brothel as a revindication of the Sons' responsibility.[1] The murderer is later caught by Daario Naharis, who finds him hiding in a wall. Daenerys pays heed to Ser Barristan Selmy's insistence that the man should have a trial for his crimes. However, Mossador believes the man does not deserve a fair trial, which leads him to finding his prison cell and killing him. Following a coordinated attack by the Sons of the Harpy, in which Ser Barristan is murdered and Commander Grey Worm is heavily injured, Daenerys decides to make peace with the Great Masters by reopening the fighting pits and arranging her own marriage to Hizdahr zo Loraq.[3][4] As expected, the Sons of the Harpy stop their attacks following the betrothal, which leads Daario to suspect Hizdahr's involvement with the group.

However, at the reopening of the fighting pits in Daznak's Pit, the Sons mount a mass attack which kills Hizdahr zo Loraq as well as many Unsullied and Civilians. During the rebellion, Daenerys, Jorah, Daario, Missandei and Tyrion try to escape the assassins by crossing the fighting pit, surrounded by a small phalanx of Unsullied. In turn, the group is quickly surounded by more of the Sons, when suddenly Drogon intervenes, burning and crushing many of them. While the remainder of the Sons retreat, Daenerys flies off on the back of the dragon, leaving her advisors and allies in the centre of the pit. While Jorah and Daario track their Queen down, Tyrion is chosen to lead the city and deal with the Sons of the Harpy until Daenerys returns, as he is the only one with experience governing a city