There's a chance Hagoromo gives this power to the edo Kage, or at least one of them.
Or perhaps Kakashi, but seeing as the Kage are in contact with Hagoromo atm, that seems more likely.
I've been writing similar threads to this one and the ones you quote for a while now. I find it funny to find other people writing pretty much the same stuff. Thanks for referencing the earlier threads as well. They've got a lot of material I hadn't seen before.
One more triad
Kannon - Amida - Seishi
I put together a thread on them. They're the Amida Triad of Pure World Buddhism. NB Seishi is the name of Kishi's twin.
You can usually trace the spread of these ideas. The Silk Route was a trading corridor that spanned from Europe to Japan. Archeologists can usually date when specific ideas and images were first conceived and map how they spread and are adapted. You end up with the same stories being told and images appearing with local variations all across Eurasia and beyond. It's nice that so many have a shared cultural history and are totally unaware of it. Kishi does a great job of retelling a lot of the old stories.
So after thinking a bit more about this, I see three people who have the potential to get the Earth seal.
1) The highest possibility is Obito because he was the Shinju Jinchuriki and might have a near death experience and meet Hamura.
Not to mention, Kishi had many chances to kill Obito but he never did, which makes me think Kishi planned this.
2) The second possibility is Sakura. She fits perfectly in the Team 7 symbolism ( See previous posts ).
The Earth seal could be Sakura's powerup ( Connected to Byakugou, See Chatte's theory) which would bring her on the level of Naruto and Sauske.
3) The third possibility is Hashirama. Hagoromo might use the Edo Hokages chakra to Rinne-tensei Hashirama removing the " being dead means not compatible with seal" point.
Problem is, Hashirama doesn't fit properly with Naruto and Sauske unlike Obito and Sakura.
Hagoromo appeared before Hashirama and talked about seals. Could it be the Earth seal ?
Point - 2 :-
Also, while this may seem like a long shot, you would have noticed that Black Zetsu removed all mention of Hamura from the tablet and the history of the legend.
If Hamura had the Earth seal which could seal Black Zetsu , it makes sense that BZ would remove Hamura from the story.
This led to the knowledge of the Earth Seal being lost and BZ would have no problems in reviving Kaguya.
Bumping this thread because I noticed something in the manga.
I theorized that this was the Earth Seal :-
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I had already made some points on how Hamura could have had the Earth Seal :-
The 'T' shaped staff (Hamura's Staff) represents Nature Energy and the unknown power and ignorance towards it. It is represented by the heavenly body, the Earth.
Since, we all live on the Earth, we rarely acknowledge it's power i.e; Natural Energy and keep on living in ignorance. When it resurfaces, it feels like an unknown power as the Rikudou's brother basically faded from history as even Madara didn't know about him.
The Rikudou's staff is the staff of peace in which the Sun or Physical Energy and the Moon or Spiritual Energy powers are counterbalanced and this brings Peace.
But the staff of Rikudou's brother has only Natural Energy. It doesn't have an opposite energy to counterbalance it. Thus, it is unstable and brings war and destruction.
Thus, the Natural Energy or the Juubi which represents the Earth was unstable and had to be sealed to prevent War.
As we know Natural Energy though unstable can be counterbalanced with Spiritual Energy and Physical Energy which is basically Sage Mode. Thus, Sage Mode might represent balance between the moon, the sun and the earth.
Since above, we assumed that the Rikudou Brother's "T" Staff represented Natural Energy and the Earth, it is possible that he was the one who controlled the Juubi's Natural Energy and sealed it within Rikudou.
Since Rikudou only has Physical Energy (Sun Staff) and Spiritual Energy (Moon Staff) and no "T" Staff (Earth Staff), it is possible that he was not able to seal the Juubi's Natural Energy and it had to be sealed by his brother who had the "T" Staff (Earth Staff).
When, the seal broke, Rikudou knew he won't be able to control the Juubi's Natural Energy and was forced to divide the Juubi into the Nine Bijuu and the Gedo Mazou and remove the Natural Energy. The Bijuu and the Gedo Mazou may be symbols of the balance between Spiritual and Physical Energy.
In the recent chapter, we got a close-up look on Hamura's staff.
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But, there is no Rinnegan like design on his staff.
And this is when I noticed something.
Notice the two points on the sides of the Earth seal ? (In blue circles)
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Looks like something was broken off from it.
The broken off piece is this :-
Taking your attention back to Hamura's staff.
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Combining the two below designs;
Rinnegan Earth Design :-
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Hamura's staff :-
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We get this :-
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Which is the true form of the Earth Seal.
For some reason; the Earth Seal broke off into two parts :-
The straight line part remained with Hamura :-
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Whereas the Concentric circle design reappears in Hashirama's Sage Mode :-
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Chatte called Hashirama's Sage Mode mark the Bindu symbol :-
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Hashirama's forehead seal, that circumpunct, is actually the Bindu symbol. What does it mean?
It represents a vast number of things, but mainly; creating life from nothingness. - Meaning, his regeneration abilities, similar to Tsunade's Byakugou, derived from Sōzō Saisei (Creation Rebirth). The Sage's technique Banbutsu Sōzō means Creation of all things. See the connection here? Basically, Tsunade creates life out of nothingness. More or less, since she does it with her chakra, but I think you get the idea.
Anyway, moving along...
Bindu is said to be located at the back of the head. This centre is said to be where the chakra is produced from, a chakra that can be the nectar of immortality. In metaphysical terms, Bindu is considered to be the point where creation begins.
In most books the Bindu chakra is not mentioned, but in the Tantra teaching a lot is written about the healing and rejuvenating effects of said chakra. It's basically considered to be the health centre of the human body and when put to use, it's said to speed up healing, satisfy the being both physically and spiritually and basically grant the user immortality.
Do you think that Juugo's ability could be the link to the possibility of the Earth Seal? His clan are the only ones to have a connection to Natural Energy/Earth without having any former training to do so. Remember that Orochimaru also created at least 6 different curse seals using Juugo's power. The most powerful of these seals were the Earth Seal (Kimimaro) and the Heaven Seal (Anko/Sasuke).
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Perhaps Juugo's clan is directly related to Hamura.
Do you think that Juugo's ability could be the link to the possibility of the Earth Seal? His clan are the only ones to have a connection to Natural Energy/Earth without having any former training to do so. Remember that Orochimaru also created at least 6 different curse seals using Juugo's power. The most powerful of these seals were the Earth Seal (Kimimaro) and the Heaven Seal (Anko/Sasuke).
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Perhaps Juugo's clan is directly related to Hamura.
The point is the Juugo Clan as well as Orochimaru's seals mixed all three powers (Body, Spirit and Nature) instead of counterbalancing them leading them to insanity and chaos instead of peace and making them sages.
In other Words :-
If you mix Body, Spirit and Nature ; You create choas, war and insanity (Juugo Clan, Orochimaru's Cursed Seals).
If you counter-balance Body, Spirit and Nature; you bring peace and become a Sage.
Bold : Reminds me of someone saying that the Heaven Seal represents the Moon and the Sun seals whereas Earth Seal is Earth.
As far, as I know Juugo's clan, Kimimaro's clan and Hyuuga's clan are all related to Hamura.
Even the Uchihas may be related to Hamura; this works as Indra was Hamura's son and was adopted by Hagoromo after his death as honour for Hamura's sacrifice. This is just pure speculation though.