Settings

Fandom settings which don't require a full book.

For original settings too minor to warrant their own books.

Planet with hereditary castes by hair color. Alicorn's setting.

https://glowfic.com/tags/197 The yeerks, a species of parasitic mind-controlling aliens have begun to invade Earth in secret. The andalites, a species of blue-furred centaurs, are trying to fend off the yeerks throughout several galaxies. They do so using the morphing power, which allows them to turn into animals- with certain limitations. A dying andalite shares this power with some human teenagers. PLOT HAPPENS. A group of androids secretly live on Earth and have the ability to store Yeerks in their heads.

The setting of the Silmarillion, the Hobbit, and the Lord of the Rings.

Buffy the Vampire Slayer setting

Near future dystopian science fiction setting where a widespread infertility crisis has lead to a rise of religious fundamentalism in the United States. Primarily owned by westwind, with additional worldbuilding by Lotus, apprenticebard, Alicorn, Kappa, hearts, and sphinx. Most writing on Cascadia was done in the short-lived Cascadiablr shadow Tumblr, although it does exist in threads and the Cascadia collection on AO3. https://archiveofourown.org/collections/Cascadia_Fiction

Planet where people can copy traits and skills from each other. By Blazing Darkness.

And similar RPGs.

Worlds in Effulgence, excluding those major enough to have their own book

Worlds in Incandescence, excluding those major enough to have their own book

Worlds within the sphere of influence of the Ofilei Trade Consortium.

Settings which are based on Pokémon, a franchise by Nintendo which includes an anime, a long-running series of video games, and a trading card game. These worlds are inhabited by creatures called pokémon. Details vary.

For George Lucas's Star Wars series, the variously canon derivative and related works, and fan-altered AUs. Overarching glowfic tag: https://glowfic.com/tags/342

Setting from swimmer963's fanfiction A Song For Two Voices of Mercedes Lackey's Valdemar series

Blazing Darkness's setting, based on Warrior Cats and... other things.

Settings large swathes of the community have done shared world and characterbuilding on.