Behind the Porcelain Mask - The Darker Secrets of the Shadowlands

From the introduction: Chaos, that is the Shadowlands. An unmeasurable swath of tarnished soil, stinking black rains and creatures that follow no laws of nature but their own. There is no ecology of Hell. There is no metaphysical logic to the element of Corruption. It takes the rules of the Celestial Order and crushes them beneath its game-balance-destroying heel.