Well, if she's dreaming of the moon, then Praxis's dreams should be of the sun. :o The Rakatsuki (the religion of the moon I created) are petty toward the Ravitaiyo (I remember telling you that i the name the Rakatsuki use to refer to the Sun's religion, but if you chose a name I don't remember it D: Sorry) so he was raised thinking that dreaming of the Sun was an omen of some sort, so it'd be pretty neat.
Anyway, I can't recall the entire idea I had for the string ('cause it was reeeaaaallly late when I got to bed), but the story Red String of Fate is Chinese and also in some Japanese myth, and since I used Japan to create the name of (and hopefully some later practices of the Shinto religion, which is also Japanese) the Rakatsuki and Ravitaiyo (AKA Raka and Ravi), I was thinking that maybe in both religions it's commonly believed that a red string tied tired around your finger was the sign of broken promise. That might sound odd, but I was just thinking about how in real life tying a string around your finger is a way to help you REMEMBER promise, so maybe both religions (since they likely have relative roots) had old traditions of shaming people with red strings to show they broke a promise or something? The symbolism here would be the Moon/Sun breaking their promise to their subjects/worshippers by harming Yggdrasil. if that's too far of a stretch, we could just say fuggit and use the Red String of Fate's lore alone 'cause that's pretty cute as is. :3