On our instance we have !cosmere@sffa.community and !brandonsanderson@sffa.community along with some other niche ones. Still working on generating content since we're so new.

Our entire instance is dedicated to Sci-Fi and Fantasy media.

There's another general fantasy one on kbin, !fantasy@kbin.social

There aren't a ton of the sub communities yet because there aren't really enough people to create content. How about !cozyfantasy@wayfarershaven.eu?