Planescape was different than what came before: This exotic AD&D setting had its own very distinct tone, art, and lingo.

TSR published a series of campaign settings for Advanced Dungeons and Dragons in the 90s. Each pushed off in a new direction. Spelljammer sent players into space and to other worlds (and campaign settings). Dark Sun was grimdark. Birthright took the classic high-level domain play and made it the centerpiece of the campaign.

Planescape started from the original AD&D “Known Planes of Existence” cosmology and expanded on it considerably, while still remaining close to the original configuration of the Great Wheel.

The Outer Planes diagram from Deities & Demigods (1980)

The Planes in the early days of gaming were typically destinations for high-level badassery (Module Q1 – Queen of the Demonweb Pits comes to mind), variations on “defeat this planar foe on their own plane”.

Planescape opened up the planes…