Cadejos appear in pairs, one white and one black. One of the pair will always be evil, the other good. The good will protect travelers from harm (especially drunks, vagabonds, and people with grudges), the evil will kill them. The good cadejo will especially protect people from evil footsteps and bad choices, while the evil one will lure them to make bad choices.

They appear as canine ungulates with goat's or deer's hooves and eyes of red flame. Some have bull horns, and all drag chains behind them. They move like deer. They can stand on their hind legs and punch with their fore legs. They range in size, but mostly, they are very large. They glitter if there is no light about. Their skin is like that of a pig.

The death of a cadejo brings a stench that lingers for days until the body vanishes. A living cadejo smells of goat, concentrated urine, and sulphur. They make a rattling noise with their throats.

Cadejos dwell in graveyards, in dark alleys, and along lonely country roads.

Evil cadejos sometimes serve the Devil, good ones sometimes serve the Honest Man. They act as scouts for these figures. A cadejo serving evil beings like the Devil is much more powerful than a cadejo serving good ones. Evil cadejos seek to gather holy relics and symbols of innocence from decent people.

Turning one's back to a cadejo or speaking to it will drive one insane. Their gaze will freeze a person. They trick people via ventriloquism, glamouring into wounded animals, causing tragic curses, taunting signs of its presence, and driving victims to madness. They do not bite, but kick and peck, beating their victims to death. Cadejos are enormously strong, almost unstoppable, save by other cadejos.

Cadejos can breed with regular dogs, breeding very strong canines that can be killed only by the strongest of men. These rot instantly if killed and leave vile stains on the ground that kills the land.

They eat bell-like flowers that grow on volcanos and new born puppies.