[Discussion] All the 4 Hokages and the Scroll could had hide the most darkest Secrets.

[Kurama999]

Maybe this should the Spoilers.

This are the privilege as being the Hokage.
This could be passed down from previous Hokage to current Hokage only.
The most darkest secret that nobody knew, except the Hokage himself.

When the 4th Hokage passed away, the alive 3rd Hokage took back his title.
The 3rd Hokage refuse to install Orochimaru as the next Hokage.
Orochimaru may come across some secrets of the Konoha, as found by Sasuke's team.

As Orochimaru did said about that those with ocular eyes could see, this was the chance that he need Sasuke's eyes to be able to see. Likewise, Sasuke said he also wanted to know.
One puzzle is that why the 1st Hokage die after fighting Madara, not killed by Madara.
Also, the 2nd Hokage, and the 4th Hokage, all passed away so young and so quickly, but not the 3rd Hokage.

So what are the dark secrets all about.
Discussion......or spoiler....

 

[Frankenstein]

Maybe this should the Spoilers.

This are the privilege as being the Hokage.
This could be passed down from previous Hokage to current Hokage only.
The most darkest secret that nobody knew, except the Hokage himself.

When the 4th Hokage passed away, the alive 3rd Hokage took back his title.
The 3rd Hokage refuse to install Orochimaru as the next Hokage.
Orochimaru may come across some secrets of the Konoha, as found by Sasuke's team.

As Orochimaru did said about that those with ocular eyes could see, this was the chance that he need Sasuke's eyes to be able to see. Likewise, Sasuke said he also wanted to know.
One puzzle is that why the 1st Hokage die after fighting Madara, not killed by Madara.
Also, the 2nd Hokage, and the 4th Hokage, all passed away so young and so quickly, but not the 3rd Hokage.

So what are the dark secrets all about.
Discussion......or spoiler....

Well they all die eventually that's no secret
As for Hiruzen, that dude was just lucky to be killed old that's no secret either.

And this is definitely not a spoiler unless you can read Kishimoto's mind but from what you wrote you obviously cannot

 

[ronus]

True. THey might have passed on darkest secret ever.
Otherwise we know almost everything. I m guessing flashbacks are on their way

 

[MarkPaul]

I agree with the secrets, but about the age when they died? Some are just lucky to live long.