Planescape is a campaign setting for the Dungeons & Dragons fantasy role-playing game, designed by Zeb Cook,[1] and published by TSR in 1994.

[3]: 98 The Outer Planes consist of: the Abyss, Acheron, Arborea, Arcadia, Baator, Beastlands, Bytopia, Carceri, Elysium, Gehenna, Gray Waste of Hades, Limbo, Mechanus, Mount Celestia, the Outlands, Pandemonium, and Ysgard.

In 1998, TSR published Faction War, an adventure that effectively closed the book on Planescape, as it was then ending the product line.

When Advanced Dungeons & Dragons 2nd edition was published, a decision was made not to include angelic or demonic creatures, and so the cosmology was largely ignored.

However, fan demand for a 2nd Edition Manual of the Planes was strong enough to justify its expansion into a full-fledged campaign setting, and so in 1994 Planescape was released.

David "Zeb" Cook developed Planescape when he was assigned to create "a complete campaign world (not just a place to visit), survivable by low-level characters, as compatible with the old Manual of the Planes as possible, filled with a feeling of vastness without overwhelming the referee, distinct from all other TSR campaigns, free of the words 'demon' and 'devil' and explainable to Marketing in 25 words or less".

[7] For inspiration, Cook listened to Pere Ubu, Philip Glass and Alexander Nevsky, read The Dictionary of the Khazars, Einstein's Dreams, and The Narrow Road to the Deep North, and for fun at "Bad Movie Nights", watched such films as Naked Lunch and Wolf Devil Woman.

Shannon Appelcline, author of Designers & Dragons, commented that while Sigil "had been largely ignored during the 3e era", it "was faring better in 4e, despite the large-scale restructuring of D&D's cosmology" due to small inclusions in the Dungeon Master's Guide (2008) and Manual of the Planes.

[14][15] Charlie Hall, for Polygon, commented that "this wouldn't be the first time that Wizards used playtest materials to tease a reboot of a classic setting".

[14] Christian Hoffer, for ComicBook.com, wrote that "while described as a collection of material from around the Multiverse, many Dungeons & Dragons fans noticed that it contained multiple references to Mechanus, Sigil, the Outlands, and other areas explored in the popular Planescape setting.

[...] Based on the last handful of public playtests, it appears that Dungeons & Dragons is gearing up for some sort of multiversal book in the near future.

[16] Pyramid magazine reviewer Scott Haring said Planescape is "the finest game world ever produced for Advanced Dungeons & Dragons".

[1] Trenton Webb of British RPG magazine Arcane called Planescape "the premier AD&D world", noting its hallmark as "a bizarre juxtaposition of legend and nightmare".

[17] Game designer Rick Swan said that the original Manual of the Planes had in a sense been "reincarnated as the Planescape setting ... TSR's most ambitious campaign world to date.

[18] Curtis D. Carbonell, in the book Dread Trident: Tabletop Role-Playing Games and the Modern Fantastic, wrote: "Planescape's sophistication marked it as D&D's answer to its own simplistic medieval-European-inspired fantasy settings, [...].

[3]: 99 In a review of The Great Modron March, Backstab magazine contributor Philippe Tessier called the presentation of Planescape products superb in general.

[19] In his 2023 book Monsters, Aliens, and Holes in the Ground, RPG historian Stu Horvath noted, "If there is a problem with Planescape, it would be its vast strangeness.

Dana Knutson developed all of the concept artwork for the setting, which Robh Ruppel turned into covers, and Tony DiTerlizzi used to fill out the interiors."