Cacus

In Roman tradition Cacus is presented as a cave‑dwelling monstrous son of Vulcan (Plutarch calls him son of Hephaestus) who terrorized the area of the Aventine Hill before the founding of Rome. In Virgilic and later retellings he steals cattle belonging to the returning Heracles; when Heracles discovers the theft he pursues Cacus, enters the cave amid smoke and fire, and kills the creature. The episode functions etiologically to explain a local cult to Hercules and the erection of an altar (the Ara Maxima) at the Forum Boarium.

Classical sources and summaries describe Cacus as a large, physically monstrous, fire‑breathing giant associated with a cave; he is said to spew fire and smoke from his lair. Medieval and later literature (for example Dante's Inferno) reimagines him as a hybrid centaur figure with a fire‑breathing dragon on his shoulders and snakes upon his equine back, but that is a later literary transformation rather than a detail of the classical accounts.

Accounts describe Cacus as able to spew fire and smoke and possessing great physical strength/size sufficient to confront Hercules. He is depicted as a cunning thief: in Virgil/Evander variants he stole eight cattle (four bulls and four cows) and concealed the theft by dragging animals by their tails to mislead trackers or, in other variants, by making cattle leave false traces. Behaviorally he is presented as a predator on humans (reports say he 'lived on human flesh' and displayed macabre trophies such as nailing victims' heads to his cave door). He is ultimately overcome when Hercules enters the smoke‑filled cave and kills him.