The Doomstones Campaign vol. 5
From the back cover:
"By uniting the four ancient Crystals of Power, the adventurers have accidentally triggered a Chaos-God's four-thousand-year plan. Now they are the only ones who can stop the stones from bringing devastation to the Old World - hut first they must learn how. And that knowledge is hidden deep in a valley occupied by worshippers of Chaos.
Between them and saving the world lie hideous mutants and Beastmen, long-destroyed Dwarfen holds, ambushes, pursuits, mad ghosts, insane cultists, Undead children, an amazing flying ship and a Dwarf who cannot die.
Determined to stop them are fanatical forces from the Empire and the Dwarfen stronghold of Karak Him, as well as the powers of Chaos who will not let the all-powerful artefacts be destroyed.
As the hole in the sky grows larger and a great storm gathers over the Yetzin Valley, can anyone survive the awful threat of the Doomstones?
Heart of Chaos is the long-awaited conclusion of the Doomstones campaign. It's an epic race against time that blends investigation, deduction, role-playing and combat with cinematic set-pieces and a heart-stopping mid-air climax. Written by the critically acclaimed games designer Robin D. Laws, this book includes descriptions of new magic, a new order of knights, game-information on the daemons of Tzeentch, and advice on writing and running all kinds of adventures. It is designed for PCs in their second or third careers."