The Sacred Tree is the God of the sacred Taisai Forest, who lives in the Taisai Temple. Because of the filthy air coming from The Kingdom, it has become weak and sick. Dorian's Ancestors sleep here, and sometimes he comes here to pray in front of his and the Wood Spirits' Ancestors. Whenever he comes to the Sacred Tree it seems to recover a little. Sometimes Dorian visits the tree to show what he learned during his training, and he thinks about the name of his thunderbolt magic, then demonstrates it.
The tree appears to be resting upon a statue of sleeping Dorian or one of his ancestors.