Hello everyone! I'm the friend in question, so I figured I should add some details. All of the monsters are based on real world mythology and folklore, which by itself is no big deal. However, I'm trying to remain as faithful as possible to the original myths in terms of both lore and statistics (though there are some exceptions; for example, aspects of one monster are based on it's theosophic interpretation). I've rarely added my own material; most of the changes have been to "sanitize" some of myths or modify them to fit into pre-existing game terms (in lots of European folklore, fey are the souls of unbaptized children or fallen angels not quite evil enough to go to Hell, neither of which really fits into D&D's conception of fey). In style, the monster entries are similar to the MM and ToB entries (I actually adopted one of my folklore monsters, the clurichaun, for the Tome of Beasts). Each entry has 300-500 words of lore and a stat block. Where applicable, I did (and will continue to) add some player-orientated information such as familiar rules and magic items. So far, there are two familiars and one magic item. This project is an intersection of my love of tinkering with D&D rules, folklore, and making monsters. There are 19 "finished" entries, a bunch more in various stages of completion, and plans for a bunch more. As I wrote them, I started thinking about ways of sharing them with a wider audience, which is how Craig and I started discussing Kickstarters. Your feedback has given me a lot to think about and is much appreciated.
BTW, here is a list of the "finished" monsters (I use "finished" in quotes because I do return to them to tinker and because I've been the only editor, though I've incorporated feedback from friends like Craig who've taken a look at them):
Abatwa Tribe - Fey (Swarm) - CR 3 - Culture: Zulu
Alicanto - Elemental - CR 1 - Culture: Chilean
Aralez - Celestial - CR 3 - Culture: Armenian
Barbegazi - Fey - CR 1/2 - Culture: Swiss (Romandy)
Baykok - Undead - CR 9 - Culture: Ojibwe
Bluecap - Fey - CR 1/4 - Culture: Northern England (Yorkshire)
Boo Hag - Undead - CR 5 - Culture: Gullah
Bubák - Fey - CR 4 - Culture: Czech
Dokkaebi - Humanoid - CR 2 - Culture: Korean
Douen - Fey - CR 1/4 - Culture: Trinidadian
Gashadokuro - Undead - CR 22 - Culture: Japanese
Ilomba - Construct - CR 1 - Culture: Lozi
Jurua - Fey - CR 1/4 - Culture: Andamanese
Klabautermann - Fey - CR 1/4 - Culture: German (North Sea/Baltic Coast)
Lechuza - Fiend - CR 6 - Culture: Tejano/Mexican (Northern Mexico)
Ouktazaun - Undead - CR 4 - Culture: Burmese
Pukis - Dragon - CR 1/4 - Culture: Latvian
Ramidreju - Monstrosity - CR 0 - Culture: Cantabrian
Sigbin - Monstrosity - CR 5 - Culture: Filipino (Visayan)
Umutwa - Fey - CR 0 - Culture: Zulu (Umutwa is a singular Abatwa)
I'm trying to have a good spread of monsters from different cultures. Upcoming monsters come from Ancient Greek, Norse, Japanese, Koori, Taureg, and Breton cultures. I'm hoping to add some more high CR monsters too.