D&D 5e Homebrew
I have played Dungeons and Dragons 5e (among other tabletop RPGs) for years as a game master. Although at the start I took heavy inspiration from the official sources, I gradually developed my own world and DM tools, including my own content, lore, and rules.
At some point I started compiling my new content into what would be a custom book. Even though I never decided to finish it, most of its would be content was already written. The book would have contained 100 spells, about 50 creatures, and more than 100 items. It would also include small lore chunks and usage recommendations for each creature.
I did finish the first part, containing all of the spells. It follows the official style guidelines of Dungeons and Dragons, and it is only missing a custom format. It can be seen here: