As with The Tower of Peng the Unprepared, this is intended to be a setting-seed for some future story or game.
The knife-tree stands tall at the top of a high cliff, a hard rock face that rises out of the woods below. The knife-tree is so called because it rises to a sharp point, limbs blown back into a shape much like a belt knife when viewed from the bottom of the cliff. It is well known as a landmark in the surrounding area, and was once a favorite lookout spot. It is now assiduously avoided. The locals swear that something odd and dangerous has nestled in its roots for the past two generations at least.
The cliff beneath the knife-tree is riddled through with caves. A few of the caves are inhabited by large and hungry beasts which roam the forest. Several of the caves were clearly once occupied by intelligent stone-workers, but none of the locals know any details beyond ancient stories of folk who lived there underground. Those stories all agree that the folk ruled the surrounding land, but beyond that they’re muddled: some claim they ruled kindly, others speak of their arbitrary nature, or their greed, or the wondrous way they had with the forest around their caverns. Each family passes on their own tales.
Regardless, the locals all agree that there used to be treasures of great value in the caves beneath the knife-tree, left by the stone-workers. They also agree that those who sought the treasure were cursed to wander ever deeper into darkness, never to be seen again. That last part may be a later addition to keep young idiots from tempting the beasts that lair in the caves, or the unknown thing which has roosted at the top of the cliff.
Potential hooks include: legends of the stone-workers, hunting ancient treasure, a hunt for the beast that lairs beneath the knife-tree, desperate locals pleading for help dealing with the beasts beneath the knife-tree, seeking a path into the dark through the stone-workers’ caverns.