On the other hand, saving Ursoc's spirit hinges on the magic contained by the sapling.
Take this torch and use it to burn the tree. You will find it in the middle of Grizzlemaw, inside Vordrassil's old trunk.
Bring me Vordrassil's ashes. It is my hope that once purified by fire, we may use its magic to cleanse Ursoc's spirit of its dark taint.
Have you brought me the ashes, <name>?
Yes! Vordrassil's magic is still present in these ashes. There might be hope for Ursoc yet.
Vordrassil's Sapling is located in the center of the old Vordrassil at [50.8, 42.7]. Be warned that the interior of the tree is a no-mount zone.