Miscellaneous Content
Miscellaneous content refers to all other minor features in Fiend Folio or subject matters not covered by other articles.
Note that many of the "unused" and "secret" content will likely never even be encountered by most players without snooping around through cheating or datamining the MOD's files, so don't expect what's found here to represent all features in Fiend Folio.
Secret and Joke Content
Hidden throughout Fiend Folio contains a variety of content whose purpose are primarily as "Easter eggs" or jokes.
The following article contains spoilers that you may wish to discover by yourself. If you feel, however, that you want to spoil it all, go ahead!
Modes
Fiend Folio features secret modes that can be turned on to alter gameplay. These modes aren't really serious and are just for fun.
Unused Content
As with any project, not everything can make the final release, and a few things have to be left on the cutting room floor.
Yeast
A folder in the mods files containing a large number of images of scrapped concepts, most of which will likely never get added to the MOD.
For the next upcoming updates, the developers at Team Folio have released a few videos on some of the fiendish foes to be found. Spoilers beware.
During the time since the Afterbirth+ version of Fiend Folio released and the MOD getting ported to Repentance through The Reheated Update, the developers at Team Folio had sporadically shared various teasers and leaks.
The following link is an archived collection of all these teasers from all around the Internet...