Many years ago (24+), I had a set of 4 Warhammer Fantasy Roleplay adventures split between 2 books.
Each adventure's goal was to try and claim an elemental gem of power. The gems were tremendously powerful, and when combined and at the end of the adventure, it was suggested the world ended.
At the time, I remember being told the adventure had been converted from a famous published D&D campaign.
I am trying to remember both the name of the WFRP adventure and the D&D campaign it may have been based on.