Myelin games made a great video about the current state of the fallen. I'm jumping on the "prince uldren United the fallen houses and we'll by allying with them later". The house of kings kell and Prince uldren had an encounter, and that's the last we ever heard of either of them. It's possible uldren killed the kell and became the new kell, and United all the houses. Theres a card about every house burning their banners, and a scannable object on titan that says "skolas attempted to unite the fallen houses but didn't succeed. Who knew that sheer desperation would succeed where he failed", as well as one on the edz that says the fallen tech has awoken/reef encryption on it. Also, purple is the color of royalty/the reef, so really all makes sense to me.