The Ilumnos Series
The settings in the red world can be split into two distinct catagories, above ground and below ground.
Above ground an enormous mountain range houses many lively active volcanoes. Lava being spewed into the sky and thick clouds of black smoke are a common sight here. Due to the geography the climate tends to be hot and dry and the air is filled with ash and embers. Most of the life above ground is animal life, the only intelligent species making home here are the gnomish refugees in the encampment of Na’er Doeh which is situated in a large valley safe from volcanoes and protected by shade.
Below ground is a maze of tunnels and caverns, some natural, others crafted by some of the many intelligent species living here. The Fire Dwarves live closest to the surface, and occupy a place between the sunny world above and what is referred to as the Underdark, which is much further below ground. The Fire Dwarves’ home is a city called Lavarus, though they have been expanding militarily and now occupy the former homes of a couple other intelligent races. The Underdark is most notably home to the Derro, the Dueregar, The Yuan-ti, the Drow, and the Mind Flayers (or Illithids) as well as other minor species and races.
Illumnos and the Red World
Ilumnos is located in an ancient ruined city atop a mountain. Though the entrance is above ground the actual room is accessed by a long winding staircase that goes into the heart of the mountain.
From Ilumnos one must use just the red crystal to get to the Red World.
Aboveground, I generally used the soundtrack from the film The Prestige