Troll Pit is a recent Danish OSR-adventure now out in English and converted from The Hinterlands RPG system (Hinterlandet) to B/X-compatible systems.
The adventure hints at the origins of goblins as strange beings born in Abyssal darkness, and for The Hinterlands it is the origin for a new spell, that only can be learned at this location.
It is a smaller dungeon, but also one intended to be visited from time to time, as it is not only a source for magic, but also a place to gain prophetic knowledge useful for other missions.
Troll Pit is not a part of the Dragon Campaign story line (Tomb of the Dragon’s Heart, Dragon Teeth of Kataphrasis and The Flooded Temple), but can easily be adapted into the storyline.
The adventure is written, so it can be played with B/X-systems such as Old-School Essentials and Labyrinth Lord, and it includes new monsters, a new spell and new magical items. The adventure also include the Hinterlands system monster stats.