Xuan Wu is an awakened form of Mystic Deep Turtle.
A Xuanwu was formed by a combination of a tortoise and a snake. More accurately speaking, it was an avatar of water, and didn’t possess a pure turtle body.
Xuan Wu is a Holy Spirit Beast.
There was a legend in Xu Sanshi’s family, that if anyone from his family could fuse with a spirit ring from a Golden Tortoise, they could possibly transform the Spirit of the entire family in a Godbeast Xuanwu Shield.