A Black Feather Counter is a type of counter used by the Synchro Monster "Black-Winged Dragon". Whenever you would take effect damage, "Black-Winged Dragon" gains a Black Feather Counter instead, but loses 700 ATK for each counter it has on it as a result. However, by removing every Black Feather Counter from "Black-Winged Dragon", you can reduce the ATK of an opposing monster by 700 points for each counter removed, while inflicting an equivalent amount of damage to your opponent.