The Gu Clan sent Xiao Xun to the Xiao Family so that she can get her hands on the Jade of the Ancient God Tuo She. In the past the clan leader of Gu Clan swore a blood oath with Xiao Xuan of not invading each others clans. In the present it seems that only Xiao Xun possess the perfect pure Dou Di blood within the past 1000 years.
Gu(古) meaning old in Chinese.
Most of Gu Clan is located in the Gu Realm which is located in the Center East Region of the Center Continent of the Dou Qi continent. More specifically, the portal that leads to Gu Realm is located there.