When the gods had lost their rule over the old world, the Sovereigns had enslaved most of them. Some had perished, while the rest had continued with the servitude. Some of them accumulated power to fight back; some had just disappeared in the sea of non-existence. The ones that had persevered to fight were the five clans as they were known throughout.
Xuanwu had chosen one from the clan he snuck into, and that chosen one had picked out two maidens from another. The original god didn't know why Shanxue wanted them, but he was very convinced of their performance. In the end, they had mastered his power and had broken the rule of the dragons.