In Roman religion , brother and sister fire deities of the early Roman settlement on the Palatine Hill.
Virgil described Cacus as the son of Vulcan and as a fire-breathing brigand who terrorized the countryside. He stole some of the giant Geryon's cattle from Hercules (see Heracles ) and hid them in his lair, but Hercules discovered Cacus's hiding place and killed him. The story is traditionally connected with the establishment of Hercules's oldest Roman place of worship, the Ara Maxima, in the Forum Boarium (cattle market).