The Blade of Spirit and Flesh, the Black Knight's core ability—as long as the enemy harbors even the slightest thought of "corruption," the Blade of Spirit and Flesh will ignore defense and inflict damage!
In other words, if your willpower isn't strong enough, even the strongest external defenses are useless...
Of course, Sig is not yet a "Black Knight," nor does he possess a true "Blade of Spirit and Flesh," but... the Promotion Ceremony has been completed—the prototype of the "Blade of Spirit and Flesh" has been forged, and it already possesses the initial power to break through defenses and fall into corruption.
Baster saw that Sea King was going to use his sword, he simply tried to defend himself, which was incredibly unlucky, as he was instantly killed!
The reason why the ritual of "Forge Blade of Spirit and Flesh" could be completed was not only due to the tireless hard work day and night, but also because Sig received another technology from Vegapunk - the fusion of objects with Devil Fruit.
When Sig completed the "Sun Path" ritual and his entire body sprouted mushrooms, he had a new idea and subsequently focused on cultivating a "Fallen Demon Mushroom"...
The technique of fusing items with Devil Fruit is not without limitations; not just any item can be used. However, the "prototype of the Blade of Spirit and Flesh," which is a fusion of Sig's flesh and will, naturally meets the requirements.
Afterwards, Sig planted a mushroom representing the authority of "corruption" on the prototype of the Blade of Spirit and Flesh, and had the Blade of Spirit and Flesh absorb it, thus completing the ritual requirements faster than expected!
And thus, he completed Sig's role as the fourth Sequence 5 – the Secret Art Master.
This method of forging the prototype of the "Blade of Spirit and Flesh" was tantamount to developing a "secret technique" and then passing it on to the prototype of the Blade of Spirit and Flesh.
Moreover, this is the purest form of "secret art" of authority developed by Sig.
It wasn't a combination of parts from Devil Fruit, but rather entirely derived from Paths of the Divine, thus becoming the final catalyst in the role of the "Secret Art Master"...
The "Sun Path" ritual indirectly aided the "The Hanged Man Path" ritual, which in turn promoted the performance of the "White Tower Path."
This is both a coincidence and an inevitability.
After all, Sig's five Paths of the Divine are originally "Adjacent Pathways." According to the advancement rules in the original Mysterious Works, not only can one risk switching between them, but the corresponding "Great Old One" Above the Sequence are also the same—the corresponding Honorific Name "God Almighty, Creator, Maker, Almighty, Lord of the Astral Sea."
To become Great Old One, besides possessing the corresponding Sefirah, one must possess the Uniqueness of all five Pathway, and have at least one Beyonder Characteristic of Sequence 1 for each of them...
Therefore, as Adjacent Pathways, it is normal for these five Pathway to have a mutually reinforcing effect.
Especially at High Sequence, the overlap of authority between them becomes more pronounced, and the effect becomes more significant!
Of course, the Great Old One are very distant for Sig. Sig doesn't even think that he can become Great Old One in this world. His current goal is only Sequence 3.
The Sequence 5 of the "White Tower Path" – "Secret Art Master" – is promoted to Sequence 4, "Prophet," whose core authority is immediately apparent: prophecy.
Prophecy, in other words, "Future Sight."
Speaking of this ability, we must mention another popular Pathway from the original Mystery series— the Fool's Path.
Sequence 9 of the Fool's Path is "The Diviner," and "divination" can also be considered as "Future Sight."
Even among the various Pathway that grant the authority to "Future Sight," the "prophet" who "passes through the White Tower" seems to be at a very high Sequence —only at Sequence 4 can one "Future Sight"...
However, the way a "prophet" Future Sight is different from that of a "diviner".
In contrast, the fortune teller's Future Sight relies entirely on Spirituality perception. In other words, if they divine something that shouldn't be divined, it's not just a matter of accuracy, but more seriously, it's extremely dangerous!
The protagonist in the original mystery also relied on a cheat-like ability to perform various reckless divinations from the very beginning...
"Prophets," on the Future Sight hand, tend to deduce the future from existing knowledge or information.
Taking this to its extreme, it's similar to the "Laplace's demon" in hypothetical physics experiments—the theory being that if an entity knew the state and position of every particle in the world, then "it" would be able to know the appearance and state of the world at any given moment in the future.
In other words, it means that as long as there is enough information, there is no such thing as "randomness" in the world. Even the thinking of all living beings is essentially a regular movement, and there is no change!
If you truly grasp all the information in the "present," you can grasp the entire "future."
If predicting the future is like gazing at the river of time against its own rules, then prophesying the future is like simulating the flow of that river of time...
It belongs to a higher and more mysterious extension of "Detective," rather than relying on Spirituality intuition.
And as expected, the ritual required Sig to "fulfill a prophecy"—similar to "Forge Blade of Spirit and Flesh," it was meant to guide Sig to actively engage with new authority.
For Sig, it would be too simple to just make a "prophecy," given his advantage of having the original work. Although Sig's own butterfly effect is significant, it still provides some guidance.
However, this kind of "prophecy" cannot complete the ritual; it can deceive others, but it cannot deceive the Paths of the Divine themselves...
Only a prophecy from a "prophet" is possible!
In other words, it involves acquiring information, making deductions, and then obtaining the "prediction content".
Sig alone was somewhat at a loss regarding the Promotion Ceremony required to become a "Secret Art Master," but he did have a clue about a solution!
"Prophecy" was an unfamiliar ability to Sig, but... Sig was no stranger to people who possessed this ability.
Madame Shyarly of Fish-Man Island, Katakuri of the Big Mom Pirates, and Basil Hawkins of the North Blue are all people with the ability of "prophecy".
In the original work, Hawkins was a fortune teller and also a user of the "Straw-Straw Fruit." Although the "Straw-Straw Fruit" doesn't have much influence on prophecy, it does have a mystical style, which might have contributed to his fortune-telling abilities...
Madame Shyarly is a great blue Fish-Man. Her prophetic abilities are innate, though she can only see a vague future. However, because her prophecies have never been Error, she is highly respected in the Ryugu Kingdom...
In addition, she is also Arlong's sister. Although Sig has never visited her, since she is Arlong's sister, she is the same as his own sister!
Needless to say, Katakuri a close relative of Sig, and Sig has personally experienced his "prophetic" abilities.
Strictly speaking, his ability is no longer "prophecy," because there's no time to "speak"—he has developed Observation Haki to its extreme, allowing him to briefly predict what will happen a few seconds later, earning him the nickname "Five-Second Man"...
In essence, Katakuri's abilities, while least like "prophecy," are the closest to those of a "prophet."
Sig figured that by targeting the three of them, he would surely gain some insight into completing the final ritual...