Thunderspire Labyrinth is the second in the three part series of adventures introducing the new 4th edition Dungeons & Dragons concept of Points of Light, a loosely connected and open-ended setting designed to allow modules and Dungeon Masters created materials to be seamlessly integrated into either a single, largely unmapped fantasy world or a Dungeon Master custom made setting. The adventure, written by Mike Mearls and Richard Baker was published in 2008 by Wizards of the Coast, as a sequel to the adventure Keep on the Shadowfell. The adventure is designed for character of levels 4-6 and the module code "H" stands for Heroic Tier. This module is set in a region of the world called the Nentir Vale, the details of which are given in the 4th edition Dungeon Master's Guide. Source: Wikipedia (en)