@sillyprince has a whole 🔗sapphic monsters list.

personally, i’ve read and can recommend: the warts & claws series by clio evans is a series of 5 novella with a mix of throuples including a MMM and a WWW book. first book is MMF and i do recommend reading in order. the second book is MFNB, so some trans rep in the series. afterglow by emily antionette is a sapphic vampire romance. second in a series but can be read a a standalone (the first book is bi4bi MF). she came from the swamp by darva green (and its sequels) are all sapphic romances with various monsters. the books vary in length from novella to novel. my summer girl by maeve black is MMFNB. mainly bringing it up for the nonbinary representation. part of a series of interconnected standalones. some of the stories in the she was mosntress anthologies are sapphic. none feature trans representation to the best of my memory though.

edited to add: @PowahWom has an 🔗achillian mosnter list that i found. i can’t vouch for most of the books as i don’t personally read a lot of achillian books but figured i’d add the link as a resource.