|“||Soon I will master this thing and be as powerful as Hermes. I’ll be able to go anywhere! I'll steal anything I want, make high quality knockoffs, and sell them around the world. I will be the lord of traveling salesmen!||”|
–Cacus, in The Demigod Diaries
Cacus was a giant that lived in a cave in the Palatine Hill of Italy in the land that would one day become the great empire of Rome. Cacus lived off the flesh of humans, and would nail their heads near the entrance of his cave. One day, Hercules passed by his cave with cattle that he had stolen from Geryon. While Hercules slept, Cacus left his cave and pulled four cows and four bulls backward by their tails so they would leave a false trail. When Hercules awoke, he took the remaining cattle past Cacus' cave and the cattle in the cave called for the cattle with Hercules, allowing Hercules to find Cacus' cave.
Cacus was so terrified that he moved a large boulder into the entrance of the cave, making Hercules unable to enter. Hercules on the other hand jumped to the top of the mountain and started tearing up the top to reach him. Cacus began breathing fire upward to try to fight Hercules off. Eventually, Hercules found the area with the largest amount of smoke and jumped down in Cacus' cave. He then strangled the giant to death and Hercules was praised throughout the land.
While Hermes delivers a package to the Roman god Janus, he falls behind on his schedule and forgets his caduceus in his truck. Cacus takes this moment to steal the caduceus and stash it to his lair underground. Not wanting to suffer the embarrassment of the other gods finding out his Symbol of Power was stolen, he pleads to Percy Jackson and Annabeth Chase for help. Annabeth, with her Video Shield, locates Cacus, but they were only able to find the entrance of his cave at High Line park in the meatpacking district of Manhattan. A square hole lined with police tape was in that area, as the day before, a construction worker was hurt when a fire broke out, but because of the Mist, the worker couldn't tell that Cacus had started the fire.
Percy and Annabeth sneak past a cop watching the entrance and climb down until they reach Cacus' underground cavern. The cavern had stacks of piping, old cars, a half sunk bulldozer, clothing everywhere, and several rotten cow carcasses, but Cacus himself was not there. Cacus soon comes into the cavern from a far tunnel, aiming to have breakfast. However, when Annabeth laughed at his appearance, he easily heard them and began to call out to them, telling them to reveal themselves. They two show themselves with their weapons out, and Cacus finds it amusing that two demigods would appear when he asked for breakfast, which Annabeth claims they are not. He begins talking about all the things he could cook them with before walking over to a cow carcass, cooking it with his flaming breath, and eating the entire thing in three bites, bones and all.
He then reveals that his cavern is actually a bargain store, as he sells everything from designer suits to watches, as well as some construction equipment that he didn't know he had. When Annabeth said that all his products were knockoffs, he admits that they are, but he steals only the best knockoffs. When Percy tries to ask (and later threaten Cacus) for Hermes' Caduceus, Cacus simply laughed at them as only Hercules had ever bested him. He then reveals that he actually has the caduceus in his hand and that he had plans for it. Shortly, Cacus learns that the snakes, George and Martha, are talking to Percy, so he orders Percy to tell them to listen to him from now on. Annabeth tries to reason with Cacus, saying that because the snakes will never listen to him, he should just give up the caduceus as it is no good to him.Cacus however didn't want to listen and said he would force them to obey. He began shaking the staff around and hit another cow carcass,accidently causing it to turn to stone. Cacus then reveals that with Hermes staff, he can travel the world to sell his knockoffs and become the god of traveling salesmen. When he turns the caduceus on Percy and Annabeth and orders the snakes to kill them, they spit out a coupon for piano lessons. Cacus then fired a warning shot over their heads to listen to him. Annabeth and Percy decide to attack him, but Cacus managed to hold off Percy with his fire breath until Annabeth stabbed him in the back of the knee with her knife. Percy then slashed his other leg with Riptide, but Cacus only yelled in pain before smacking Percy with his hand and almost stabbing him with the caduceus. Annabeth then hit him with her shield, but he took it from her and crumpled it like paper. He then pointed the caduceus at Annabeth, but the snakes transformed it into a cell phone as it began to ring.
He shook the caduceus again and they went back into their regular form. As Cacus got ready to land the finishing blow against Percy and Annabeth, Percy flooded the cavern with thousands of gallons from the New York sewage system. Cacus survived however and managed to figure out Laser Mode on the caduceus, climbing out of the tunnel with what looked like a bazooka. Cacus chased them into the park, firing laser blasts every now and then trying to hit them while offering people damp,fake Rolexes. When Cacus caught up with Percy, he walked up to him and asked if he had any last words. Before firing, the caduceus turned into credit card scanner and he tossed it to the ground in anger. Percy used that moment to run past the giant and take the caduceus back.
Just then, Annabeth dropped the claw of a crane down and it hit Cacus in the head. Annabeth then grabbed Cacus with the claw and flung him in the air. George and Martha then went into Laser Mode again and Percy blasted the giant into dust. While returning the caduceus to Hermes, they mention that Cacus wasn't the one to come up with the plan to steal his caduceus and wanted to cut off the gods communication lines. Hermes fines this a bit ironic as Zeus had been threatening to close Olympus, but he doesn't tell the two demigods this. When asked what Cacus meant about other enemies, Hermes only mentions that the gods have many enemies.
Cacus is very underhanded and somewhat lazy. Despite being a son of Hephaestus, he prefers to steal things instead of making them himself. In fact, he only steals knockoffs of things and not the real thing. He is quick to anger and feels that no other demigod could defeat him as only Hercules was ever able to. When faced with a problem he can't solve, he tends to use force instead of using his brain.
Cacus stands at about ten feet tall, making him a small giant when compared to others. He has curly orange hair and orange freckles, as well as pale skin, leading Annabeth to call him the "ginger giant." His face has a permanent pout, an upturned nose, wide eyes, and arched eyebrows so he looked unhappy and startled at the same time. He wore a red velour housecoat that he kept open, revealing silky Valentine-patterned boxer shorts, with a pair of slippers that matched his coat. His chest was also covered in a patch of hair that was a combination of red, pink, and orange.
- Cacus is able to breath fire, as well as being fireproof himself.
- Cacus is very sneaky, being able to steal from the god of thieves, Hermes. It should be noted, however, that Hermes had been distracted at that moment.
- Despite being a smaller giant, he has very enhanced physical strength.
- Cacus has excellent hearing.
- Being a son of Hephaestus, Cacus could make anything he wanted to thanks to the gifts he inherited from his father. However, he just finds it easier to steal things.
- Despite Cacus normally being a figure in Roman mythology, as he lived in the land that would become Rome, he refers to himself as a son of Hephaestus. However, he refers to Hercules by his Roman name.