Battle between two brothers

In the land of Serpentania there were two brothers: Yin and Yang. Yang was the brother who was white as snow, he had long neck and a purple symbol of harmony on his head. He was the brother of harmony and light. But Yin was purple and his heart was black as night. He wanted to rule Serpentania. Their dad, who was the ruler of the Serpentania had decided, that the next ruler would be Yang. So Yin  challenged Yang. Yin wasn't powerful enough to win this battle. Yang made a half of Serpentania dark, where Yin was expelled and he had to live there.