Yin She Shi Yan was a faction of the Hunter Assocation in Kai Sa City. Li Tao was a part of it.
After being betrayed by Lin Xuan Chi the Sabbat annihilated the Faction.
Li Tao believed herself to be the last survivor, and died thinking that.
The had a secret base in the hills called Crescent Pearl Inn.
In truth, there was another survivor, who left the Faction before the attack of the Sabbat. He helped Zhao Yan to find Yue Jian who was taken to the hills.