side-quest-ish and open-ended to be sure.
A recently re-discovered odd treatise
In the chosen families, the son was always more dangerous than the father.
As long as a hundred spears and longer, the weapon must be hoisted!
The Sneel are causing trouble again.
Not quite Science Fiction…
Someone wants Prince Philoj dead. Or?
Wherever the PCs have gone recently, they have heard the talk. The Doomsday Machine of Toothless Amalgam has stopped spitting out birdseed. The End is nigh.
Shadows gather…and linger.
The Age of Vog…The Unending Winter of Discontent, The Epoch of Smoke and Ash.
Everyone can think of a favorite song or two (or three) which can easily be translated into a fantasy rpg concept, be it an item, plot, location, or what have you. Just take the lyrics of your favorite real-life ditty, and go from there!
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...