The Mountain of Fire, otherwise known as the Isle of the Lepers, was the home of the Untainted, a group of barbarians who had lived through the barbarian war with the wizards. It was made up of a mountain surrounded by a lake of lava. In order to cross, a wooden bridge was lowered by hill giants kept by the Untainted for labour. Those who failed to provide the correct proof of passage or broke the laws of hospitality were barred from the mountain.
It was also the storage place of the last reserves of rune essence, taken from the wizards and guarded by the Untainted. During the Misthalin-Morytania war of 164, some of the essence was stolen by a trio of guests sent to retrieve the essence to cleanse the Salve. Shortly afterwards, a party from the Wizards' Tower attacked, stealing all the essence and sacking the place. What became of the Untainted afterwards is unknown.