I think this is partially broken now (at least when you skip, which for some reason is always required between versions). Skipping to endgame means you have to "go to cellar to talk to Illiana," but that seems impossible once some part of the day has passed. So you can't sleep without going to the cellar, but can't go to the cellar if you already sent Nyx. Brilliant design!
Edit: Actually, I guess I'm missing the gem for the mirror, but I can't seem to get it by skipping. Still clearly something bugged, I guess.