Cacodemons are the manifestation of a person’s worst memories created by Nyx, and as such are technically the "children" of her and that person. According to Dolus, they count as very, very, very minor gods.
The Nico di Angelo Adventures[]
The Sun and the Star: A Nico di Angelo Adventure[]
After freeing Bob, Nico di Angelo comes face to face with half a dozen cacodemons Nyx created shortly after the son of Hades entered the Underworld. He inspects them and sees his worst memories resurface. Nyx takes this as a sign Nico is destined to be consumed by trauma. Nico attacks Nyx but they do nothing to aid the goddess until Will Solace gives her hay fever and they swarm the son of Apollo. Nico manages to take control of them and free them from both his and Nyx's control. They later return to Camp Half-Blood with the son of Hades, who nicknames his "Cocoa Puffs".
The Court of the Dead[]
The cacodemons accompany Nico and Will to Camp Jupiter. They later play a vital role in the Battle of Golden Gate Park, merging back into Nico along with Semele to help him withstand the Mist being shattered. When Nico tries to shatter the chains holding Dolus and Apate, the impact drives the Coco Puffs back out of him. Dolus reveals to a stunned Nico that as a form of daimon, the Coco Puffs count as very, very, very minor gods, meaning that their agreement alongside Semele's in freeing the two bound gods counts as a vote of a council of gods. With the Coco Puffs chewing on the chains, Nico is able to cut them and free the two gods. When Dolus and Apate go overboard with the Mist, the Coco Puffs guide the Greek and Roman demigods through it.
Description[]
Cacodemons vary greatly in appearance- some are more humanoid than others, some have multiple legs or tusks or antlers, some have single eyes-but always resemble three dimensional shadows with glowing eyes. As seen with Defiance, cacodemons are able to open their mouths wider than should be possible.