Four Against the Forsaken Depths

From BoardGameGeek:

Delve into the bowels of Norindaal and level up your heroes! This book has all the rules for the Heroic and Legendary adventuring Tiers, and describes the lethal dangers and limitless riches of the Forsaken Depths. Heroic skills, including Heroic spells. Legendary Skills,including Legendary spells. Heroic and Legendary magic treasures. Full profiles for all the monsters that dwell in the bowels of Norindaal. Map and content generators for the Six Rivers of the Forsaken Depths, the Citadels and the fearsome Cyclopean Idols. New tiles for underground dungeons and for the Six Rivers. This book requires a copy of Four Against Darkness and Four Against the Abyss. A D10 and a D12 are required in addition to the standard D6s.