who rules the plains between demacia and noxus?

When mousing over demacia and noxus on the new map it becomes clear that theres a large swath of what looks like fertile land between the two kingdoms. The only other large unassigned area on any of the major continents is the jungles east of shurima but that land is likely more or less untraversable for average humans so I get that it is left to those that naturally reside there but the plains between demacia and noxus look like prime farm land and seem to have a clear path to the freljord so I dont really get why they are left unclaimed on the map. Perhaps there are other unnamed factions similar to arbormark? Idk but I hope they fill it in eventually.