Despite Tyrion's urging to spare them and send them to the Wall, Daenerys keeps her word and has Drogon immolate them, which convinces the other prisoners to bend the knee.
Despite Tyrion's urging to spare them and send them to the Wall, Daenerys keeps her word, and immolates them by use of Drogon's firebreath. This convinces the other prisoners to bend the knee.