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.
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.