The Darkening! It's coming! I cannot hold it back. […] Nothing can be done. Thra calls me home. […] The Darkening is pure energy. It cannot be destroyed. […] Like all energy, it can only be transferred, moved! […] Blessing or curse, I do not know. But my power… is yours.The Sanctuary Tree's last words to Deet
Perched on the hills that roll down from the Mountains of Grot is a wise old tree with pink petals and roots going down to the caverns underneath. When the wind is right, the petals from this tree can fly to almost anywhere in the Skarith Region.
As Deet escaped from a hostile Nurloc and found her way to the Sanctuary Tree, the latter began to speak, explaining to her that the reason behind the creature's aggressive behavior is due to it being infected with the Darkening. And, that the Great Trees have tried to contain the energy from spreading. But now, it was too powerful to restrain, and expanded to nearly most of Thra. The tree then gave Deet a vision of all life becoming tainted and insane before she fainted.
After Deet recovered from the event, she was then tasked to warn the All-Maudra of the Darkening by Maudra Argot, who is aware of the Sanctuary Tree's sentience after the former told her about the tree speaking to her. The Great Tree later helped Deet to be transported to the surface of the mountains.
Aughra after departing from the Castle of the Crystal was led to the Great Tree by urVa to help the crone restore her connection with the Song of Thra. After trying several ways to hear the Song only to end in failure, Aughra became fustrated at her inability. However she fell into despair upon encountering a Darkened creature, and with no way to heal it, she begged the Sanctuary Tree to help her. The Great Tree complied and purified the sickness, Aughra humbled and now seeing that she could not forcibly hear the Song decide that she would wait by her friend until Thra spoke to her.
Later, when the Arathim and the Grottan Gelfling escaped from the caverns infested with the Darkening, the Sanctuary Tree was not be able to, as corrupted Nurlocs ravenously consumed its roots ; however, the tree still had enough strength to pass on his power to Deet before withering away into decay.