The Otherworld / Old World:
Home to the Balrogs, the otherworld is a realm of fire and darkness. It is supposedly a land of demons and war. However this information clashes with that, which is that Balrogs were Maiar, who existed before Arda, and are of the same order as Gandalf, Sauron and Saruman. Wherether the story has been mixed through various folklore throughout the ages of Middle-earth, just like the destination of the One Ring story, is unclear, though these demonic balrogs were the most feared in the Morgoth realms, so a Balrog customised land may have been created.
"It is a Balrog. A creature of the otherworld." Gandalf the grey.