Every demon in the show is not only a soldier, but an officer commanding troops as part of an actual, tangible military force that is doing genocide. Like they're not even settler colonialists bringing and settling civilians alongside them, they're the actual formal military of an invading genocidal empire, who are uniformed and engaging in atrocities in uniform. They're also explicitly elite forces, with even the weakest of them being akin to elite human warriors or mages. The only "child" demon is a small one that some humans tried to raise as a pet.