I actually didn't catch that and it was one of the few twists that surprised me. Once Black Face started talking with Wakamoto's voice I figured it was Mumuka from the intro but I thought somehow they transferred the soul into the robot or something. For some reason I didn't put 2 & 2 together about how Monado couldn't cut people & so the robots put people in them. I actually think it was pretty smart of Takahashi only showcasing/mentioning that fact (that Monado can't cut people) once at the very start, so you kind of forget it and then 40-50 hours later when they reveal the twist you go "ooooh"
I was geniunely surprised!
What I did think was pretty predictable was most of the other main plot stuff. Especially since the visions show what's going to happen. You knew that the emperor was going to die and that since the black face was mumuka and the white face was white + girl that it was going to be fiornne.
Although otoh, I think the visions give the story potential to actually be surprised when the future is changed. Like when Odama in colony 6 didn't die and Rein saved him I was geniunely surprised because having the old elder guy sacrifice himself and die and the hero be helpless to stop it is a very cliche thing so you were expecting that to happen. But it doesn't! And that's surprising. But then it does with the emperor, so it's cliche lol. On one hand it feels cliche and on the other hand it means next time you're going to be unsure of whether the vision will happen or be stopped. I think it works. I get the feeling leading up to the ending you'll see visions of it and see a bad ending over and over and then when you change it into a good ending it'll be a satisfying finale. That's my guess at least.
But the reason I really like Takahashi's stories and why I'm loving Xenoblade is that even within the predictable events (going to the top tower, king is going to die, fiornne is going to be the white mech) there's still been a ton of unpredictable events and mysteries in the world lore. The other prophet guy, Meinus, Zanza, the mysteries of the Haenter race and their high technology. Why monado and the giant were sealed. The most interesting parts so far have been the scene when Miera becomes qualified to be the next emperor and the AI talks to her and says her mixed blood of haenter & holme is what they ancients wanted and what can free them from the giant's curse & the stuff with the prophet + zanza where they talk about how zanza was full of shit and all that was all just an act & the part where meinus talks to zanza and he's like "how can this be?! Oh, you are on who is outside the circle of events" & meinus talking about how El someone (who I'm guessing is the true form of the prophet guy) doesn't realize she exists yet.
Anyhow, I'm going to put forth my current theory on the story from what we've seen through the end of prison island.
I think the story is about a never ending circle of events like Xenosaga/Gears where every thousands of years the Giant God and the Machine God have the lifeforms that have grown up from them fight and kill each other as a sacrifice to resurrect the gods so they can do battle again and then they die which kills everything on them and rebirths life from the ether of their dead bodies and the cycle starts again.
I think that the prophet guy is the spirit of the Giant God itself. And Zanza is his helper/underling/the actual Monado sword. They are all putting on an act like they do everytime with the humans to lead them toward their demise and the rebirth of the gods.
Meanwhile Meinus, like Elly in Xenogears is some immortal god or person or something who is outside this circle of events and everytime the circle happens she tries to stop it but is killed (like Elly's true soul) and her goal is this time (like previous times) to try to stop the chain of events. And her comment about them not having realized its her, meant that the prophet hasn't realized meinus has been reborn yet and it's her chance to sneak around and try to influence the events.
And the wildcard is shulk. Why choose him for the Monado? Like Meinus said, why unlock the power of the Monado to slice humans when it will be detrimental for Zanza (I'm guessing because it can now slice him)? I don't have any ideas here and I'm looking forward to what they do with it.
Of course my theory is heavily banking that Takahashi is pulling another Xenogears/Xenosaga endless cycle of death/rebirth with reincarnated souls who attempt to stop it. So maybe he isn't and it's nothing like that
But Takahashi loves his Evangelion style plotlines, so it might be! :lol
I'm almost pretty curious about the hienter ancients, because one of the npcs in their city said originally the hienter watched the battle of the gods from outside of the fight looking on in and then after the fight concluded they flew and landed on the kyoshin's head and built their city. Definitely curious about where this whole battle of the gods is taking place.
But yeah, all in all there's a lot of meat in the story & world. Lots of questions. It's been a long time since I've played an rpg as interesting as this. Really looking forward to how it plays it in the 2nd half (I'm assuming the prison tower cutscenes are the midway plot-twist of the tale).