In summary: Kaido and Doflamingo are (or were, in Doflamingo’s case) both working for Shiki, as were Higurashi and Semimaru, which allowed Kaido to obtain himself a base of operations in Onigashima.
You might ask: “if Kaido and Higurashi were working together (under Shiki), why did Kaido kill her?” Well, after Higurashi had done her part to install Orochi in power in Wano, she had outlived her usefulness; likely also is that after she interfered with Kaido’s fight, he was positively itching for a chance to get rid of her (like Luffy, Kaido seems to hate people interfering with his fights). Not only that, but if Shiki wanted to go into hiding, why would he let Higurashi, who can mimic his appearance, wander around freely? Crocodile did a similar thing by only interacting with his subordinates through a proxy (Nico Robin).
As for Semimaru, after Kaido killed Oden and Orochi was safely in power; he too had outlived his usefulness.
Isn’t it strange that both the Mane Mane no Mi and the Bari Bari no Mi ended up in East Blue, the weakest sea that Shiki had no respect for? The sea where, more than any other, Devil Fruits are so rare that some people haven’t even heard of them and those who have consider them myths even then.
So, has Shiki shown the world hell? Well, if he’s the mastermind of the Smile plot like I think he is, then:
- He enabled the Human Trafficking Ring in Sabaody (that was being run by Doflamingo).
- He led to the enslavement of the Tontatta at Doflamingo’s hands for Shiki’s scheme; in fact, Doflamingo probably even sought out Dressrosa because the Tontatta were there and Shiki needed their miraculous botanical expertise for his plot.
- He had a drug created that looks like a fruit, but either turns you into a monster or gives you brain damage, either way it takes away your ability to swim (and unlike Devil Fruits there is far less of an upside to eating a SMILE).
- He allowed Caesar Clown to do everything he did in the Punk Hazard arc (and his crimes constitute a very long list).
- Allowed Kurozumi Orochi to do everything he’s doing in Wano. Since Higurashi and Semimaru infiltrated Wano 41 years ago, Orochi might be fulfilling a much, much older version of Shiki’s plan (creation of large amounts of weapons) without realising where the plan came from. Higurashi’s claim of being a Kurozumi may or may not be lies, but it being true doesn’t stop her still being a former member of the Rocks or Golden Lion Pirates.
Shiki intends to do the same that happened to Wano at Orochi and Kaido’s hand to other countries around the world.
As a final note, “Golden Lion”, this in an interesting epithet for Shiki to have.
- Lions are “the King of Beasts”, obviously. The Thousand Sunny’s figurehead is a Lion for a reason (the fact that it’s also a “sun” ties into the “Dawn” motif that pops up every now and then). There actually isn’t much in mythology about Dragons ruling, and when they do they do so as part of a group (such as the Azure Dragon of Chinese mythology).
- Gold is also used as a mark of achieving great heights in One Piece.
- Gol D. Roger AKA Gold Roger, was the King of the Pirates.
- Gold allowed Enel to reach the Fairy Vearth.
- Luffy ringing the Golden Bell, which was high above Skypeia, ushered in a new era for the Sky Island (and changed Bellamy’s outlook on life for the better).
This paints a picture of the epithet “Golden Lion” being a very grandiose title, a title for someone to soar above all others as the “King (of Beasts)”.
I hope this theory was a fun to read as it was for me to write.
*Theory by Pidmik