Brimstone

Brimstone /brimˌstōn/ is an extremely hard and black rocky material found only in Shimetsukeru, where it completely covers the surface. Brimstone is used in the construction of everything in Shimetsukeru, as well as some weapons carried by some high ranking Demons in the Old Order. Brimstone only be altered by the Demon King and select individuals designated by them, or in some cases, someone just as strong as the Demon King (e.g. Kazega Eijizoyo with Xiphos).

Some areas in Shimetsukeru appear to have a black substance similar to dirt but it is actually finely powered form of Brimstone, called Brimsoil, giving it the same feel as ordinary dirt; the same can also be said for Brimsand, which is a coarsely ground version of Brimstone. There is no metal variant of Brimstone, nor is there any metals in Shimetsukeru.

In some Jigoku jails there are Brimstone pillars that have glowing texts inscribed onto them, these pillars prevent passage of any beings besides Demons that attempt to pass the face with writing; because of this, all pillars have the writing facing inward from the perimeter.