Having to put up with the threat of Cacodooms for so long, some Big M'ungus decided that it was finally time to take action, and after doing research on the ancient Ultimate M'ungus Machine, Citadel, and genetic modification in general, decided to capture a couple Cacodooms. They modified these Cacodooms to the point they were close to their size, and barely aggressive, too, instead being extremely friendly, and only being aggressive towards other Dooms. They dubbed their creation the 'Cacodoomer' and created many different forms of them, the main differences being size, color, proportions, eye color, and spike number. Cacodoomers are pets owned by Big M'ungus all over the Gas Planet, and also serve to protect them against Cacodooms and other Dooms that may try eating their owners. Their forelimbs are long and wing-like and help them move efficiently through the skies of the Gas Planet, while their legs are short and clawed to allow them to perch on surfaces. Their mouth may be lined with uneven, jagged teeth, though these are only for grabbing and holding onto prey, be it their whole body, or just a chunk they tore out. Their mouth contains an extendable tongue similar to a frog's and dog's combined, which allows them to easily eat and drink from containers. They have many soft, feathers like spikes on their body, which are mainly to look cuter.

They are very curious, cuddly, and oddly soft and fun to touch, having a surface texture similar to fuzz. They enjoy getting pet, and will try snuggling up to their owners at times, making them great for emotional support. They can also emit a sort of purring sound from their bodies. They love flying around outside, and it is advised that they are taken out at least once a week to avoid them going crazy inside. Other than being a pet, they are also voracious predators and defenders, and are extremely aggressive towards Cacodooms and their non-domestic relatives, flying over and landing on top of them as soon as they see one, before attempting to tear them apart. Even when having a full stomach, Cacodoomers will tear prey to shreds, and only seem to not act this way against the food they are given by their owners; a close relative of them that instead of a pet, was modified to be a sort of kibble for them, which they just lap up when hungry. Due to their curious and cuddly nature, they love the company of other Cacodoomers, and may try snuggling up and playing with each other if in the same area. It is important that they are played with daily, or they may become hyperactive and/or depressed. If abused, Cacodoomers may become feral, and may try leaving its owner, becoming an aggressive stray, which are hard to rehabilitate. They produce barely any spite, so they are not much of a threat towards their owner, though it is still advised to not consume any part of them, no matter what it is. Due to their method of reproduction, they have been modified so that they have to be given a specific nutrients so that they can reproduce, and this is used to easily breed them together, though, this nutrients can also be made from specific compounds found in Poolloons, so some Cacodoomers have learned they can eat Poolloons to produce spores.