You must all know who the Dark Avatar is. New, and more exciting rumors are coming in about him. Rumors that suggest, he is real.
I. Identity of the Dark Avatar;
A character we havent seen yet...he is lurking in the shadows.
II.??Creation of the Dark Avatar;
When Aang was released from the iceberg, Yin and Yang started to turn again. Aang is obviously Yang (light) and the energy from his Avatar State spirit, contains anger, agression, and evil.
As seen in Book 2: Chapter 11, when Aang faces off against the sandbenders. When Aang was discovered, the true evil inside him, must have overwhelmed him, and the spirit, flew into someone else.
But the real question his....who?
III. His Appearance, When Will He Show?
That is a good question. After Aang has defeated the Fire Lord, he will possibly step out of the shadows, and confront his doppleganger. Or maybe he is already among them, waiting.
This is what I've heard.