The eldest child of Typhon and Echidna, Cerberus is the only one who works for the Olympians directly, being fiercely loyal to his master Hades. Cerberus has three heads and one body and likes to play with Mrs. O'Leary and rubber balls. He was tamed by Psyche using rice cakes and Orpheus using music. Cerberus is also sometimes affiliated with the Graco-Egyptian god Serapis.
The Twelfth Labor of Hercules
For Hercules' twelfth (sometimes eleventh) labor, he was ordered by King Eurystheus to bring back Cerberus as proof of his strength and fearlessness. Hercules eventually found the entrance to the Underworld and entered, but rather than attack Cerberus on sight, Hercules, who had heard many stories of Hades and how he treated intruders, ignored the infernal monster (who let him pass) and continued straight onward to Hades' Palace.
Hera's plan to pit Hercules against a furious Hades backfired, when the hero humbly knelt before the terrifying Lord of the Dead, and asked permission to take Cerberus. Hades was impressed by Hercules, who until then had an infamous reputation for acting without thinking, and while all heroes who had previously entered the Underworld did so to win fame, Hercules was the first to place respect for Hades above his own ambitions. Hades was so impressed with this, that he granted the demigod permission to take Cerberus on a few conditions. The first was that Hercules could not seriously injure Cerberus, and thus, could not use his weapons against him. The second condition was that Hercules had to bring Cerberus back as soon as the labor was completed. The third and final condition, was that the hero had to tell Hades who had asked him to bring back Cerberus as a trophy. Hercules promptly agreed to all of the terms, and told Hades, that King Eurystheus had asked the labor of him.
Thus, placing aside his mighty club and deadly Hydra arrows, Hercules returned to Cerberus to wrestle the beast barehanded. Cerberus was tremendously strong and fierce, his three heads biting and snarling rapidly. The combatants seemed evenly matched, and fought so fiercely that earth cracked beneath them and walls shook. In the end, however, Hercules managed to headlock and slowly drag Cerberus out of the Underworld, back to King Eurythseus. The king was terrified when Hercules returned, as he had not expected the hero to return from what he believed to be a suicide mission. The people of the kingdom ran in fear and panic as Hercules approached with the ferocious infernal monster. Hercules casually asked where Eurystheus wanted his knew trophy, but was turned away by the fearful king, who took cover. Hercules asked if Eurystheus was satisfied with his labor, to which Eurystheus proclaimed fervently that he was, and for Hercules to get the beast out of his kingdom. As he had promised Hades, Hercules escorted Cerberus all the way back to the Underworld, after which the mighty monster returned to his duties.
Percy Jackson, Grover Underwood, and Annabeth Chase encounter Cerberus and Annabeth manages to "tame" him by using a large red ball and some skills she learned at obedience school. Annabeth plays with Cerberus using the red rubber ball while Percy and Grover sneak past him. After Cerberus chomped the rubber ball, Annabeth tells him that they will play again someday and goes through, although she wipes a tear from her cheek because she knew that she could never come back and play with him.
Later, when speaking with Hades himself, Percy mentions to him that he should play with Cerberus more often, noting that his uncle's pet dog has a special affinity for red rubber balls. This innocent comment, however, only enrages Hades more.
Mrs. O'Leary plays with Cerberus when Percy and Nico di Angelo are in the Underworld, trying to carry out their plan for Percy to jump in the River Styx. Percy notes that next to him, the gigantic hellhound looks like a petite puppy. Fortunately for the demigods, Cerberus does not follow Percy and Nico to the River Styx, even though he wants Mrs. O'Leary to come back and play some more.
When confronted by Annabeth Chase and Sadie Kane, the Greco-Egyptian god Serapis reveals that when he took over the Underworld, he transformed Cerberus into his staff which is destroyed in the battle that follows to stop Serapis, presumably returning Cerberus to his original state in the process.
Despite being terrifying and fiercely dedicated to his duty, Cerberus is quite docile, playing with rubber balls with Annabeth in The Lightning Thief, readily accepting cakes from Psyche in Percy Jackson's Greek Heroes, and quickly socializing with Mrs. O'Leary inThe Last Olympian. He also has a good relationship with his mistress Persephone, and is fiercely loyal to his master Hades.
Cerberus is described as a terrifying and gigantic black Rottweiler, easily dwarfing even the biggest Hellhound, since Percy Jackson claimed that Mrs. O'Leary (whose size is comparable that of a garbage truck) is a petite puppy if compared to Cerberus in terms of size and stature (which makes sense, as Cerberus did father all Hellhounds, making all other Hellhounds his puppies). Cerberus wears a chain collar with three holes and has blood-red eyes and razor-sharp teeth and nails. Cerberus is also semi-transparent (he grows more visible the closer you are to death). Cerberus' barks were loud enough to make Percy's "eyeballs rattle." Cerberus also had a snake like tail.
- Along with Kampê, and Ladon, Cerberus is one of the few monsters that Percy is too terrified to engage in combat.
- Cerberus is, quite possibly, the most powerful son of Typhon and Echidna, being a very formidable foe, even for Hercules himself.
- Despite his ferocity and reputation, he is actually one of the few "good" monsters, as he is one who is used by the gods as a force for good rather than evil.
- It is believed that he misses his mother and feels sympathy for her; however, if she ever were to show up and ask him to rejoin the Titans' or Giants' cause with her, it is likely that he would refuse.
- In some myths, Cerberus also has snakes protruding from parts of his body.
- According to Percy Jackson's Greek Gods, Cerberus has the ability to eat the souls of the dead.
- There may be more than one Cerberus as Serapis reveals in The Staff of Serapis that when he took over the Underworld after the Greeks took over Egypt, he transformed Cerberus into his staff which he had until Annabeth Chase destroyed it to defeat Serapis.
- His Norse counterpart is Garm.