Ma Costa was a feared and respected Gyptian woman with a hawk dæmon. Her family was noted for its grandeur and sumptuousness, known as "princes" among the other gyptians.
Ma Costa cared for Lyra Silvertongue as a baby and hid her from Edward Coulter. Lyra and her friends once stole Ma Costa's houseboat.
During the Horse Fair many years later, her son Billy Costa was kidnapped by the gobblers. She remained strong-willed and never gave up looking for him.