In the Avatar State, the Avatar channels the power of all their past lives and becomes capable of feats of incredible power and destruction.
While the Avatar State is a necessary tool for protecting the world from great threats, it also poses a great risk to the Avatar themselves.
If the Avatar loses control of the Avatar State, they can become consumed by its power and turn into a destructive force known as the Dark Avatar. The Dark Avatar is a being of pure chaos and rage that is capable of wiping out entire nations.
Avatars must learn to control and master the Avatar State in order to use its power for good and prevent it from becoming destructive.