Beyond the Prime's infinite crystal spheres, beyond the endless realms of the Outer Planes, lies the absolute reality of the Inner Planes.
The cornerstone planes of Air, Earth, Fire, and Water are the most well-know Inner Planes, but they're only the beginning. From the deadly purity of the Positive and Negative Energy Planes to the unbearable filth of the Plane of Ooze to the eternal storm of the Plane of Lightning, the Elemental Planes are the substance of existence itself. These eighteen planes for the foundation of the entire multiverse: they are the cauldron from which all energy and matter are brewed.
The Inner Planes (1998), by Monte Cook with William Connors, is the final major sourcebook for the Planescape line. It was published in November 1998.
Origins (I): Farewell to Planescape. After four and a half years, the popular Planescape line came to an end with The Inner Planes (1998), as Wizards of the Coast ruthlessly cut back on the many settings that may have been one of the factors in TSR's downfall.
But, The Inner Planes wasn't a bad stopping point for Planescape, as all of the major parts of the Great Wheel had now been covered in: Planes of Chaos (1994), Planes of Law (1995), In the Cage: A Guide to Sigil (1995), Planes of Conflict (1995), A Guide to the Astral Plane (1996), A Guide to the Ethereal Plane (1998), and finally The Inner Planes (1998).
Meanwhile, Wizards of the Coast had already plotted out an alternative path that would allow for the publication of a few Planescape-adjacent projects in the last few years of AD&D 2e. "A Paladin in Hell" (1998) had appeared just a few months earlier as a planes-related adventure that didn't have Planescape branding. Three similarly related supplements would follow, beginning with Warriors of Heaven (1999), a companion to Planescape's Faces of Evil: The Fiends (1997).
Origins (II): A History of the Inner Planes. The Inner Planes is almost entirely devoted to the many elemental pages, with short digressions to the Positive Energy Plane and the Negative Energy Plane.
Gary Gygax says that the original elemental planes were drawn "from Aristotelian physics, but then leaped ahead some centuries to [Paracelsus] and later Spiritualist writers." However, the elemental planes didn't get much use in Gygax's original Greyhawk campaign because "none [of his players] were sufficiently powerful to survive such journeys"; instead, the closest they got was probably the elemental nodes in T1-4: The Temple of Elemental Evil (1985).
Fans of D&D first found out about these planes in The Dragon #8 (July 1977), which described them as "the ultra-pure Elemental Planes of air, fire, earth and water."
Novelist Jeff Swycaffer then came up with a new idea for the elemental planes in The Dragon #27 (July 1979), suggesting that additional planes could appear between the main elemental planes. The idea was sound, but his planes of cold, moist, hot, and dry didn't stick. He also replaced the positive and negative planes with good and evil, which introduced yet more confluences, creating the elemental planes of begin, fertile, light, and pleasure (next to good) and barren, dark, end, and pain (next to evil). Again, the core idea would influence the game, but not the specifics.
In The Dragon #32 (December 1979), Gygax acknowledged Swycaffer's article, saying: "It is of interest to relate that just prior to the appearance of the excellent article … Dave Sutherland and I were discussing the various Elemental Planes, concentrating on the borderland areas betwen them, i.e. where Water touches Air and Earth and where Fire touches Air and Earth. Mr. Swycaffer’s ideas were good indeed, and if vapor is substituted for 'moist' and dust is used to replace the term 'dry/dryness,' you will have a good idea".
Gygax's reinvented elemental planes appeared in Deities & Demigods (1980), with four "para-elemental planes": ice (between air and water), dust (between air and fire), heat (between fire and earth), and vapor (between earth and water). It took Gygax a few more years to finish off the inner planes. That began with EX2: "The Land Beyond the Magic Mirror" (1983), which featured "a quasi-elemental monster, a lightning elemental from the Elemental Plane of Air—or perhaps from the border where that plane touches the Positive Material Plane." Dragon #73 (May 1983) gave the full details, when Gygax added eight quasi-elemental planes: lightning, mineral, radiance, and steam lie between the elemental planes and the positive material plane while ash, dust, salts, and vacuum lie adjacent to the negative material plane.
There were a few things in that article which didn't become a part of the canon: its cubic nature and the introduction of planes for "shadow" and "time". However, the inner planes as they evolved through The Dragon #8, Deities & Demigods, and Dragon #73 was otherwise the model for the planes of The Inner Planes. Ironically, The Inner Planes was nearly the last depiction of the Inner Planes in this state; the para- and quasi-elemental planes would disappear with the publication of Manual of the Planes (2001) for D&D 3e (2000).
Adventure Tropes: Hostile Elements. Adventuring in the elemental planes was always a problem in the early days of D&D. As Gygax said, characters had to be high level. Even The Inner Planes admits the elemental planes are "hostile environments", creating a "survival problem". That's because "ultra-pure" elemental planes require characters to survive fire, water, magma, or what not. The Inner Planes offers solutions to this problem by outlining spells and magic items that can help characters to survive.
Exploring the Great Wheel. The Inner Planes is the best description ever of the majority of the Inner Planes, far exceeding the shorter sections in the original Manual of the Planes (1987). It details the elemental planes, the para-elemental planes, the quasi-elemental planes, the positive material plane< and the negative material plane.
About the Creators. Cook wrote many of the most pivotal Planescape products from 1995-1998, beginning with Planes of Conflict (1995) and ending with Faction War (1998) and The Inner Planes (1998). Next up: D&D 3e!
About the Product Historian
The history of this product was researched and written by Shannon Appelcline, the editor-in-chief of RPGnet and the author of Designers & Dragons - a history of the roleplaying industry told one company at a time. Please feel free to mail corrections, comments, and additions to firstname.lastname@example.org.