From publisher blurb:
Go to Hell!
Originally planned as a setting supplement for 3.5, Internal Adventures has returned from the ashes for players and game masters alike. This guide draws on the rich mythology of Milton’s Paradise Lost and Dante’s Inferno to provide an overview of life and death in the Nine Circles of Infernus. It includes everything from rules for impiety to new arms and armor, new feats and flaws to dozens of new magic items and spells.
Venture down through the Nine Circles into the inhospitable wilds of Limbus, the windswept maze of pleasure and pain of Salax, the festering swamp of Golos, the industrial nightmare of Avarus, the floating prison ships of Styx, the endless cities of Retic, the burning river and deserts of Phlegethon, the ten tortures of the Malebolge, and the wind-swept wastes of the ultimate traitor in Cocytus. This complete setting contains 13 species and 35 subspecies, 28 feats, 31 magic items, 36 spells, and 55 subclasses.
What the hell are you waiting for? Damnation is just the beginning. Infernal Adventures await!