Bytopia

In the Dungeons & Dragons fantasy role-playing game, Bytopia, also known as the Twin Paradises, (bi- + utopia) or, more fully, the Twin Paradises of Bytopia, is a lawful good/neutral good aligned plane of existence. It is one of a number of alignment-based Outer Planes that form part of the standard Dungeons & Dragons (D&D) cosmology, used in the Planescape, Greyhawk, and some editions of the Forgotten Realms campaign settings.

Bytopia is a virtuous plane of cultivated beauty, and is home to many of the deities of the gnomish pantheon.

The plane known as the Twin Paradises was mentioned for the first time by name in the article "Planes: The Concepts of Spatial, Temporal and Physical Relationships in D&D", in The Dragon #8, released July 1977. In the article Gary Gygax describes the plane as one of the "Typical higher planes". The plane was mentioned again in an appendix of the known planes of existence in the original (1st edition) AD&D Players Handbook, published in June 1978, where it was described as "The Twin Paradises of neutral good lawfuls".

Bytopia is a spatially infinite plane, consisting of two layers or sub-planes. It is unique in the sense that the two layers are laid facing one another, each looking down (or up; the terms are relative here) at the other. A traveller can look up from one layer and see the other above him looking back down (or, from the other side's perspective, up), provided that the sky is clear. To get from one layer to the other, travellers must either climb tall mountains, or fly. Gravity reverses when someone reaches the middle point between the two layers. Bytopia shares its borders with the neighbouring planes of the Seven Mounting Heavens of Celestia and the Blessed Fields of Elysium; travel is possible between Bytopia and these planes at certain locations.

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Wikipedia