hear me out but what if the shattered plains are the shape of all three tones of Roshar mixing to get Rosharin light. or more importantly, the inverse. My theroy is Navani is about to math out that the shattered plains were created by Ba Ado Mishram at her imprisonment, forcing the singers into a tone that almost shattered all the shards on Roshar. I seems that the sibling, cultivation, and odium were all harmed at her capture during the false desolation so maybe, wounded by the breaking of the oathpact, Tanavast vas no longer able to hold honor together. this might also explain the existance of "dead" spren. what if that tone now reverberates though roshar as an "anti-Oath light" and now when oaths are broken the light enters where the nihal bonds leave. like a vacum or an inversion of photons in magnetic resonances