Oooh! I can't write for the fandom, but your ideas about how Adelis and Desdemona might work together ring bells in my head - have you read Harrow the Ninth? If not, I recommend it - the Locked Tomb series' ideas about the River would make for a fabulous blending! ♥

Hope you get what you want! I've requested Desdemona and Sugane, myself. ^_^