Correct me if I'm wrong, but I feel this is relevant information.
Edo-Tensei is a technique that brings someone back from the dead, granted that their soul has not been sealed (or, in certain cases, their soul has been put at rest.) If one tries to summon someone that cannot be summoned, the edo-tensei will fail (as seen during the Orochimaru-Sarutobi fight.) Thus, in a sense, an edo-tensei can be used to check the status of a soul - Alive, Summoned, or Sealed/At Rest.
Kabuto has advanced knowledge, and has seemed to have brought every decent ninja back from the dead - Seemingly, most people that could fight at a jounin level or better. Granted that the DNA of most ninjas has been easily accessible, he has summoned them all.
Bottom line - Why hasn't he summoned Izuna (one of the few that have managed to unlock all of the abilities of the sharingan, apart from having an EMS?) I believe that he tried to summon Izuna, yet failed since Izuna's soul is already in the living world. That's a part of the reason that he knows who Tobi was this whole time - Izuna's soul was somewhere amongst the living.
"They were mine to begin with" - Izuna's eyes, transplanted to Madara, and given to Nagato by the revived Izuna. Literally, the eyes were originally Izuna's/Tobi's, so no argument there.
This man is not edo-tensei'd... When he is hurt, some white Zetsu-like material comes out. If it was edo-tensei, his arm would regenerate immediately. He does fear death, seeing as he avoids getting attacked.
He's someone that Madara knows, and trusts enough to transplant the Rinnegan into Nagato. Think about it... Do you really expect Madara to transplant his own eyes? The transplant has to occur post-mortem too, according to the rules of edo-tensei; If Madara comes back with the rinnegan, he died with the rinnegan. Dead man transplanting eyes? woah.
Rinne Tensei seems to be a one-use type of deal (one use, and can revive any amount of people, to a certain extent)... I'm thinking this because Tobi was talking of it as such.
My theory of events...
1. Madara brought back Izuna (using some method,) and added some Zetsu attributes to him. After this, they decided on a plan - revenge on Konoha, taking the Kyuubi, reviving the heretical demon statue, and the moon eye plan.
2. Madara used rinne tensei to revive the Heretical Demon Statue (which is a living being now,) causing his death. Izuna (Tobi) had to implant the rinnegan (and ideals,) into Nagato, who would eventually serve the role of reviving Madara (at the cost of his own life via Rinne Tensei.) Izuna decided to attack and seize the Kyuubi when the time was right - aka, the birth of Naruto (when the seal was at its weakest.) The plan failed, and Izuna started using Akatsuki to retrieve the tailed beasts.
3. Kabuto eventually used edo-tensei, failing to bring back Izuna, and managing to bring back Madara (who died with the Rinnegan, indicating that the Rinnegan transplant occurred post-mortem.) Madara thought that it was Nagato's rinne tensei that brought him back, and was shocked that it was edo tensei.
Tobi is Izuna (who is alive by some means,) and he is indeed working with Madara. Madara's death was caused by the rinne tensei, which had to be used to bring the heretical demon statue to life, in order to complete their plans.
Edo-Tensei is a technique that brings someone back from the dead, granted that their soul has not been sealed (or, in certain cases, their soul has been put at rest.) If one tries to summon someone that cannot be summoned, the edo-tensei will fail (as seen during the Orochimaru-Sarutobi fight.) Thus, in a sense, an edo-tensei can be used to check the status of a soul - Alive, Summoned, or Sealed/At Rest.
Kabuto has advanced knowledge, and has seemed to have brought every decent ninja back from the dead - Seemingly, most people that could fight at a jounin level or better. Granted that the DNA of most ninjas has been easily accessible, he has summoned them all.
Bottom line - Why hasn't he summoned Izuna (one of the few that have managed to unlock all of the abilities of the sharingan, apart from having an EMS?) I believe that he tried to summon Izuna, yet failed since Izuna's soul is already in the living world. That's a part of the reason that he knows who Tobi was this whole time - Izuna's soul was somewhere amongst the living.
"They were mine to begin with" - Izuna's eyes, transplanted to Madara, and given to Nagato by the revived Izuna. Literally, the eyes were originally Izuna's/Tobi's, so no argument there.
This man is not edo-tensei'd... When he is hurt, some white Zetsu-like material comes out. If it was edo-tensei, his arm would regenerate immediately. He does fear death, seeing as he avoids getting attacked.
He's someone that Madara knows, and trusts enough to transplant the Rinnegan into Nagato. Think about it... Do you really expect Madara to transplant his own eyes? The transplant has to occur post-mortem too, according to the rules of edo-tensei; If Madara comes back with the rinnegan, he died with the rinnegan. Dead man transplanting eyes? woah.
Rinne Tensei seems to be a one-use type of deal (one use, and can revive any amount of people, to a certain extent)... I'm thinking this because Tobi was talking of it as such.
My theory of events...
1. Madara brought back Izuna (using some method,) and added some Zetsu attributes to him. After this, they decided on a plan - revenge on Konoha, taking the Kyuubi, reviving the heretical demon statue, and the moon eye plan.
2. Madara used rinne tensei to revive the Heretical Demon Statue (which is a living being now,) causing his death. Izuna (Tobi) had to implant the rinnegan (and ideals,) into Nagato, who would eventually serve the role of reviving Madara (at the cost of his own life via Rinne Tensei.) Izuna decided to attack and seize the Kyuubi when the time was right - aka, the birth of Naruto (when the seal was at its weakest.) The plan failed, and Izuna started using Akatsuki to retrieve the tailed beasts.
3. Kabuto eventually used edo-tensei, failing to bring back Izuna, and managing to bring back Madara (who died with the Rinnegan, indicating that the Rinnegan transplant occurred post-mortem.) Madara thought that it was Nagato's rinne tensei that brought him back, and was shocked that it was edo tensei.
Tobi is Izuna (who is alive by some means,) and he is indeed working with Madara. Madara's death was caused by the rinne tensei, which had to be used to bring the heretical demon statue to life, in order to complete their plans.
