My Theory on the truth of Madara. (Spoilers!!)
I've seen a lot of predictions pop up for whats really happening with Tobi, who he is, why Madara has been summoned as an Edo Tensai. Some of them are very far-fetched, others are well thought out but it'd hard to imagine someone as insignificant as Kagami Uchiha could suddenly have one of the biggest roles in the entire show. I have a new theory i'd like to put forth based on everything i've seen without even suggesting that Tobi is some random Uchiha (wow) lol.
I'd like to remind people, that when Tobi tussled with Danzos henchmen, his arm was infected and had to rip it off but it wasn't bloody and gory, rather it was white. This 'Tobi' person has always claimed to "Have the power of Uchiha Madara" and there is every chance he does. He also said he was a "shell of his former self" which is why he doesn't get into much combat as he is weak. I've had this long standing theory for a while, and with the latest Manga chapter, ive decided to share it.
Tobi is a Zetsu Clone of Madara.
Lets assume for a minute, that Madara has known Zetsu a long time. With White Zetsus now being shown to perfectly take over someone, and copy them perfectly, with the same dna, chakra network, kekkai genkai and abilities, it makes sense. Zetsu himself is weak, which is why 'Tobi' is always avoiding battle and teleporting around the place. It also explains why the arm he tore off was white, and why he's now grown it back.
Two possibly scenarios exist here. The first, is that on his death after he fought the 1st Hokage, Zetsu (who always watches lol) was asked to take the last of his chakra and his life in order for his 'Moons Eye' plan to live-on. He could carry out his wishes with all of his abilities, tho he'd obviously be a lot weaker thanks to just being a clone. The other option of course, is that Zetsu at the very end betrayed him, took his powers and his identity, and is now carrying on with his own plans. He often referrs to having Madaras powers in the third person, something Madara himself would be unlikely to do.
Itachi implanted the Amaterasu in Sasuke to self-activate on seeing Madara. Therefore, the man under the mask has to look like Madara, so my zetsu theory also explains the self-activation of Amaterasu.
So how come this possible clone knows Izanagi? Zetsu himself is some sore of freaky plant-based thing, possibly born from experimentation of the Uchiha to gain the power of the Senju. He travels through the earth and through wood, making it perfectly possibly he somehow has a connection to the Senju, whether he has thier powers or was somehow born from the firsts jutsu i don't know, but it would explain how he can use Izanagi since he absorbed the Uchiha dna from Madara, but was possibly derived from the Wood Jutsu.
I think at this stage in the Manga, Kishi would be arrogant to introduce some random uchiha who just happens to have one of the biggest roles in the show, it would piss off a lot of fans to be honest. Now for me to be a little far-fetched. Perhaps, if Zetsu is able to take someones chakra and make a perfect clone, if he does that to the point where the victim dies, i wonder if its possible that the soul of the person is also absorbed, meaning that this zetsu clone really does contain the soul of Madara, kinda like a temporary body. He spoke about becoming "complete" when he told about the Moons Eye plan. He may have anticipated that someone would bring his body back or he had plans to do it himself when he was strong enough after the moons eye plan was complete, but he needed a temporary body to extend his life, one that could regenerate and stay alive longer. There is still much speculation but i'd love to hear your thoughts.