Cacus
2 of the 7 encyclopedias on this shelf carry an entry for Cacus. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
ka'kus, in Roman legend, a giant, son of Vulcan. He lived in Italy on Mount Aventine, one of the seven hills of Rome. When Hercules was bringing the red oxen of Geryon from Spain, he rested near the dwelling place of Cacus. The giant admired the oxen and, while Hercules slept, stole a part of them. In order that Hercules might not be able to trace them by their footprints Cacus drew them backward by the tails into his cave. This stratagem was successful, and Hercules would have lost his oxen had they not lowed in response to the lowing of the rest of the herd as Hercules drove them past the cave. Although Cacus was a giant and had three heads, Hercules strangled the monster and recovered his bright oxen. Sancho Panza , in Cervantes' Don Quixote , alludes to the stealing of the oxen when he says of Rinaldo, "There be greater thieves than Cacus." See Hercules
1000 Classical Characters (1900)
A famous robber, son of Vulcan and Medusa , represented as a three-headed monster vomiting flames. He resided in Italy, and the avenues of his cave were covered with human bones. When Hercules returned from the conquest of Geryon, Cacus stole some of his cows, and Hercules, discovering the theft, strangled Cacus in his cave. 2026 Editor's Note: While this text identifies Cacus as the son of Medusa , other mythological traditions describe him as the son of Vulcan or Hephaestus. The theft of the cattle occurred after Hercules defeated the giant Geryon , who was the actual grandson of Medusa. The conflict is famously depicted in the 16th-century sculpture Hercules and Cacus by Baccio Bandinelli, which stands in Florence's Piazza della Signoria. (Ed: BR 2026-06-29)