I think it's a kinjutsu that was used against the Juubi or maybe Madara knows creation of all things.. shit I don't know:nuts:
As Madara has shown us, he ALWAYS has a back-up plan in case something happens, not to mention the guy knows more about Jutsu's then even their creator's know (i.e. - Edo Tensei). That being said, I think Madara's trump card will be some form of sealing technique that will allow him to control the Jinchuuriki/Obito or some form of kinjutsu similar to that. This is Madara we are talking about... the guy has defeated the 5 current Kage with ease, planned for backfires in his long-term plan such as if Nagato had double-crossed him/them, and oh yeah.... has pretty much controlled history behind the scenes for decades+ and was able to come up with a scheme so detailed that makes Einstein look dumb. (Had Einstein been a Manga character that is =D)
Or he could always just use that original jutsu of his that most have forgotten about AKA send like 500 comets Obito's way since the guy has unlimited Chakra :devil:
EDIT: Also, much like Hashi was able to immobilize the Ten-Tails in his Sage-Mode, maybe Madara has created a Mokuton so powerful that it would will immobilize Obito.
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It looks like Madara is getting ready to summon something, also I wanted to point out that Obito didn't fully absorb the Ten-Tails or put simply, absorb it in it's Final Form:
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And since Obito is walking around like a zombie as if he took in too much power already and seems like he has no idea what is going on (or else he would have killed Madara first since he just tried killing him/using him for his own selfish desire), I would guess Madara's trump-card is going to be some multi-chapter, 2000-step process.
