This was the jutsu used to summon the 1st and 2nd...
* Name: Summoning: Impure World Resurrection (口寄せ・穢土転生, Kuchiyose: Edo Tensei; Viz "Summoning: Worldly Resurrection", English TV "Summoning Jutsu: Reanimation")
* Type: Kinjutsu, S-rank, Supplementary[1]
* User: Orochimaru
* Hand Seals: Tiger → Snake → Dog → Dragon
* Debut (Anime): Naruto Episode 69
* Debut (Manga): Chapter 117
Summoning: Impure World Resurrection is a forbidden technique used to revive the dead. The ninja will first sacrifice a living person to provide the vessel that the dead soul will inhabit. The dead body will then be encased in ash and dirt to resemble the original body of the person that was resurrected. When the ninja wishes to recall the souls, a portal will open in the ground and the caskets holding the bodies will appear. When the caskets open the bodies will be gray and in a state of minor decay, requiring a special seal to restore their appearance. At this point, the revived person remembers their former lives, and thus is not under the user's control. The same seal used to restore their appearance also wipes the soul of its free will, putting them under the user's control. This technique can also be used to summon multiple people at once, depending on the amount of sacrifices and the chakra level of the user.
Once complete, the revived is impossible to kill by normal means. If a limb is destroyed or removed, it will simply regenerate. To kill the revived, the soul has to be removed. When the Third fought against the revived First and Second Hokages, he had to create shadow clones and perform the Dead Demon Consuming Seal on both of them to kill them. In doing so, the bodies turned back to ash and dust, with the bodies of the individuals sacrificed to lay among the ashes.
reference from Wikia:
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Summoning: Worldly Resurrection
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We see here Orochimaru places a seal behind their heads
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The 2nd can use 2 high level jutsu's Suiton Suijinheki, Suiton Suiryudan
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The 1st Hokage
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using Mokuton Jyukai Koudan
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and also used
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(the Darkness Jutsu)
If the 3rd didnt use Fuuin Jutsu Shiki Fuujin (The Death God Jutsu)... no way would he have been able to beat the 1st or 2nd... at the level they seemed to have...
but I dont think the 1st and 2nd Hokage were at they full strength when fighting the 3rd...
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