Not sure if it's necessary to spoiler-tag Quinn. Anyways...you lost me on the whole wave thing, some level of backstory that I'm missing/forgot. Also I could have sworn it was not a given that any Adept can see Joule, but I may be off (been playing as Copen a lot as of late).
On the 80% ending:
[spoiler]Transcript
Xiao: Thanks for giving me a lift to the Garden. So the Glaive is... Er, you made it a pendant?
Nori: It's cuter that way.
Xiao: I didn't expect you to care about cute.
Nori: I'm full of surprises.
Xiao: Um...ha ha? Anyway, we have what we came for. Thanks.
Nori: You merged Joule and Mytyl and woke the power of the Muse. Then you extracted the activated Septima essence. What are you plotting here?
Xiao: No plot! It's just... The Muse has so much power. Eden shouldn't have it. And neither should GV. Plus it would make Mytyl's life miserable. So by using this Glaive... er, pendant... we can seal the power away and let her live in peace. Er, don't you know all this? Isn't it why you helped?
Nori: I need to be sure.
Xiao: Mytyl's father cut out her Septima. Sumeragi turned her Septima into a living Glaive--Joule. This damaged Mytyl's physical being as well. But now, maybe she can start to live.
Nori: You're just telling me what I want to hear. What are * your* objectives here?
Xiao: Nothing bad, I promise. You'll know more soon.
Nori: .....
Nori clearly states that Xiao was behind the merger, which happened mid-battle between Copen and GV. There's a lack of consistent direction in how Mytyl and Joule's memories progress. When Mytyl first wakes she appears to be reacting on instinct to somebody's defeat (whoever you're not playing as), never moving her body beyond the basic Septimal levitation, and never responding to questions from GV or Copen mid-battle. After the battle, she gets up, and is coherent, clearly improved from her mid-battle status. In GV's case she actually refers to him by his nickname even though she's defending Copen. But after two sentences or so, her memories leave her abruptly. It is extremely sudden and comes off as a complete 180 from how she had been progressing thus far.
I find that suspect. We know that Mytyl was damaged the first time the Muse was extracted from her, and that the Muse can assimilate the memories of its host, as it did with Joule when she was shot. I find it no small stretch that the memory loss is a result of the Septima being extracted.[/spoiler]
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