“ 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...”
“ An intelligent mask that, when worn, takes control of the individual and mimics their personality, only to commit horrendous crimes and commit great acts of evil in secret.”
“ There are crimes for which a man is not killed, but chased into the wilds, away from his home and country, to not return or be killed on the spot. In one culture is the condemned mutilated, and even his vocal cords are damaged so that the voice is unrecognizable to his friends and family. This is the punishment for people too obsessed with their own prestige.”