HOW do i get o mushins tower floor 9????

[Oblivypony]

I cant seem to find a quest for it all the portals for it are locked and I have defeated the three mushins on floor 8 so what am I doing wrong????

I am getting frustrated as i am wasting time on the call to arms even any information would be greatly appreciated as I dont understand why all the portals are locked I have to be missing a lteer quest somewhere or something,,,,,