Under very special circumstances, it is possible for a Chao to evolve into a Chaos Chao. Chaos Chao are named after the beast Chaos, from the first Sonic Adventure game. The Neutral, Hero and Dark Chaos Chao are called the Light Chao, Angel Chao, and Devil Chao respectively.
Chaos Chao are very unique in that they are immortal; they will never die nor reincarnate, no matter what. Once your Chao succeeds in transforming into a legendary Chaos Chao, it will stay in that form forever. You should therefore choose wisely before pursuing this transformation; in particular for the modern versions, you will not be able to raise your Chao’s stat grades after it transforms.
As immortal Chao, Chaos Chao have no need to reproduce and therefore cannot mate. Make sure that if you create a Chaos Chao that you won’t want to breed that particular Chao in the future.
A final attribute of Chaos Chao is they do not retain animal parts like regular Chao, or have different eyes/mouths. All Chaos Chao are pure and take on a single, featureless appearance.
There are four general requirements that your Chao must satisfy in order to transform into a Chaos Chao. There is also a fifth alignment requirement if you want to get a specific kind of Chaos Chao. Once all steps are complete, when your Chao goes into a cocoon, special music will play and a Chaos Chao will emerge!
On Sonic Adventure for Dreamcast, you can only obtain the Light Chao as there are no Hero and Dark alignments!
- Your Chao must have reincarnated at least twice. This means it must be on its third life or more.
- Your Chao must have over 50 happiness. Happiness is a hidden value which runs from -100 to 100, and it is increased by caring for your Chao well. Your Chao must have had over 30 happiness to reincarnate in SADX, and over 80 in SA2.
- You must give your Chao at least one of every animal in its current life. Contrary to popular belief, you can give your Chao more than one of each animal. In other words, your Chao must have learnt every animal behaviour. The animals that you have given to your Chao in its previous lives will have no effect on this.
- Your Chao must be balanced, so that it would otherwise evolve into a Normal type. Your Chao must not be set to evolve into a Swim, Fly, Run, or Power type. This is how the false belief that you must give only one of each animal came about. Giving an equal amount of each animal is the easiest way to ensure this requirement, though.
- If you want a Neutral Chaos Chao, otherwise known as the Light Chao, then your Chao must be of the Neutral alignment. Care for your Chao by using a mixture of Hero and Dark characters.
- If you want a Hero Chaos Chao, otherwise known as the Angel Chao, then your Chao must be of the Hero alignment. Care for your Chao by using mostly Hero characters.
- If you want a Dark Chaos Chao, otherwise known as the Devil Chao, then your Chao must be of the Dark alignment. Care for your Chao by using mostly Dark characters.