More accurately, the Inferno is a collection of planes rather than a single plane. These planes are the home of a loose oligarchy of demon princes. One such demon prince, known to history as Pazuzu, sided with the Triumvirate during the War of Humanity. Another demon of note is Indrani, modern-day Goddess of Sin and former demon general. Denizens of the Inferno speak a language called Qith.
In general, the populace of Achaea lacks the means to travel to the Inferno. However, it is known that the Apostates are allowed access to a small portion of this plane (presumably along its border) through their demonic skills. In this place, on an unassuming island amid an inky-black lake, is an immense pile of charred, broken bones of the innocent. Upon this pile rests a throne carved from a single slab of obsidian. Blazing a fiery crimson in the firmament above, hellish daemons circle through the flames on leathery wings.