The Cadou were created from nematodes exposed to the Mold and were visually similar to the Black God that lay at the heart of the fungal super colony. They were the brainchild of Mother Miranda, a mutant who sought to create a counterpart that would become host to a preserved copy of her daughter's conscious mind. Human experimentation with Cadou was extensive though largely unrewarding, with many hosts either dying or turning into Lycans. Over time, however, at least eight test subjects survived on with superhuman abilities, and began aiding Miranda in pursuing parallel research, being themselves unsuitable as hosts for Eva.
Cadou, like the Black God, assimilate the DNA of a host, and will alter the host to incorporate DNA from other organisms they have assimilated. The location of implantation varies, though it is uncertain if any change results from this; both head and abdominal surgery were methods used.[note 1] Any foreign DNA within the host's body could also be assimilated by the Cadou and spliced into the host genome. Examples include the Dimitrescu daughters, who took on the ability to transform between mutant humans and fly swarms, and the Vârcolac who were humans contaminated with wolf blood. Cadou implantation can be very dangerous for the host, and often results in death within days. Those that do survive may turn into mutants such as Lycans, who were seen as failed adaptations in her superhuman project.
Cadou are also noted to be able to control sub-colonies of their own, and are able to survive when bisected. In the case of Donna Beneviento, the half in her body could control the other half planted within her doll, Angie, and was able to make the doll move on Beneviento's command. After contaminating the plants in her garden, Beneviento was also able to produce hallucinogenic pollen and influence its effects on enemies. Both the Angie Cadou and the plants died following the death of Beneviento, who was stabbed in the head where her Cadou was.
"Cadou" is a Romanian word which means "gift", which is a borrowing of French "cadeau" of the same meaning, itself from Old Occitan "capdel" meaning "ornament".
In the Japanese version of Miranda's Diary, it is established these are nematodes (線虫,senchū?). Worm-like organisms can also be seen protruding in some Cadou-infected subjects such as Salvatore Moreau and Uriaș Străjer.