I'm really curious as to what Sasuke's EMS is going to look like. Madara's EMS looked like a combination of his Mangekyo and his brother's.
Sasukes Mangekyo is already so busy, I can't imagine trying to add Itachi's to it and not having it look terrible.
Obviously it was his Mangekyo power. We know using it twice in a row almost kills him.
But you know what, now that you brought that up, wtf is with Madara just going "Don't bother using that on me, it won't work." and Kakashi just BELIEVES HIM.
I mean, I know most attacks pass through Madara, but Kakashi's power makes tiny fucking black holes. That might be the kind of thing you can't phase through!
"Naruto, don't bother hitting me with a Rasenshuriken. I'm totally immune to it."
"Really?! Now what willl I do!"
While I agree that the backstory says combines, that thing in that picture isn't really there. It's one of Itachi's illusions.