I recall I once theorized that the Akatsuki's leader and the 4th were involved together on the kyuubi summonning,,, I guess I still have it.

points to take notice off:
-Minato (4th) knew about the Kyuubi/Madare realtion beforehand, that's why he created the death god seal.
-the 1st probably sealed part of the Kyuubi itself into the amulet that Naruto has, which is why it's a conductor of energy.
-"that" jutsu is probably the death god seal, only this time, Naruto will really take the demon to the grave.
-since it was said that the wind country (sand village) has created the Shukaku priest seal to match out the Kyuubi of the fire country, and we know that Shukaku has been around for quite a while, it's likely to believe that Madare has found a way to limit the kyuubi's "spawnning point" to the land of fire, perhaps by creating a giant tsukiyomi and bringning sadness and anger to it.
-chackra types: if minato has only sealed the bad energy and left the good energy to be used by Naruto, it means that the bad energy is also the part of the demon that Naruto talks to, and when the sepertion is broken, the kyuubi will get a bit of personnality balance, and willl become a mentor charecter (I bet he's pissed at Madare for sticking him inside the smelly country).