"How is he? Will my son ever recover from the bugs that turned his brain to mush?"
The doctor pointed to where the thirty-seven year old was playing with toys on the floor. "It's been five years now and he has the brain of a child, give it another five and we can start the basics of teaching him magic again. He knows who you are but...but he will never have the same personality again, and by the time he regains all his magic skills at their former levels he will be in his sixties."
And in the name of the great and powerful I command thee to return to your body, hearth and soul, so that you might walk again and continue in the gods plans.
See that. . . wait. . . what!?! NO! I knew it was too risky here. You have brought ruin to us all. Why you ask? Ready your weapon, a traveler has come.
-Father Hayden, performing a ritual on the deceased outside the protection of the church.
With a huge number of sacrificial victims, another realm long ago secretly bound a Prince of the land spirits, Iorstonn by name, thus ensuring the fertility, and improving the magical defences, of their realm. But binding that Prince to one spot has disrupted the weather and magical patterns (ley lines?) over half the continent. Things have become bad enough that a coalition has been formed to rectify the situation, once divinations have established the cause.
Your party is one of the teams assembled to do the rectification: find the binding object and steal it ("so that we can destroy it here in our realm, of course"...*) or destroy it over there. Presumably the Prince will be grateful to his rescuers and angry at the binders, but with a greater spirit like Iorstonn one can never be sure: such beings are "tricksy".
* Of course, the rulers of our realm might want to control Iorstonn for their own ends...