"You'll have to excuse Frederic... he hasn't been the same after... well, you remember."
-Subrhone Malfes Sternbrugge, Custodian of Prince Fredric van Heinhelm.
"If the OD-RSDs were here already, the facility would have gone up in smoke a long time ago..."
"This is Skybase Alpha-One broadcasting to Skybase Alpha-Two through Six. Seventeen point zero VD-TD Drop Ships inbound towards Korolis Sector, Quadrant Two. ETA approximate - 0030 hours. Recalibrating Ground Ordinance to avoid excess Friendly Fire. Reaffirming aerial perimeters and air supremacy..."
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...