“ Found written on a torn single page...
'Lay thee patiently and still upon the ground, contemplating the Leper Star in the firmament, 'neath a crescent moon, midst the graves of a boneyard 'til the G'na-Shennu come crawling up from the foetid earth. Fear them not. Let them rage about thee, casting ghoul-dust from their chalky talons and scalps,'til they calm, and so begin to whisper their secrets. Then shall they solemnly withdraw into the earth once more, in peace.'”
“ In one region of a forest, all of the trees are identical, down to the leaves and the twigs. If the PCs carve something into one of the trees, it could mystically propigate until it covered all of the trees, or could vanish since it was not carved into the one true tree.”
“ 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...”