Unlike the Crystalmists to the immediate north, the Hellfurnaces feature many active volcanoes, allegedly ignited in the time of the Rain of Colorless Fire. These peaks are accurately described as a hive of evil, a treacherous landscape made worse by the presence of giants and fire-loving abominations. The steep walls of the Hellfurnaces are reliably reputed to hide many cavernous entrances to the Underdark. On the good side, the Hellfurnaces shield the Flanaess from the horrors of the Sea of Dust, beyond to the west. The legendary Passage of Slerotin, a straight tunnel from the Yeomanry to the ashen wasteland, was recently discovered here and is being (slowly) explored.