From the introduction: A blighted subterranean sandbox. ... "O, blighted Gehennom, that fetid, fungal vale, that under-city of mouldering crows and sullen ghosts... Deep, deep beneath where the Khemri raised their towers, deeper than even the deep-holds of the Gholon, where the fires burn downwards... Gehennom, where the hearts of those who dwell within are darker than a Rukh's coal-black pinions..."