In chapter 907, Garp talked about a crew nicknamed “Rocks” who were prominent 40 years ago, before the Pirate King Gol D. Roger came into power, he even said that he could not imagine what the Marines would do if they came back into power.
Garp is connected to them in some way as he got the distinction of “Hero of the Marines” from dealing with them.
Hina said that they lost their captain. I believe their captain was Rock, just like Luffy’s crew is called Straw Hats, Roger crew is called Roger Pirates, Shanks’ is Red Hair Pirates … their crew was nicknamed after their captain.
I have finally found the pirate Oda got inspired from regarding Rock. Oda got inspired from Roche Braziliano, which in English translates to ” Rock the Brazilian “. He was a Dutch pirate born in 1630. His pirate career lasted from 1654 until his disappearance around 1671.
Rock the Brazilian was a very cruel pirate. He led a mutiny. A munity is a criminal conspiracy among a group of people, typically a crew of a ship, to openly oppose a lawful authority to which they are subject.
In Rock’s very first adventure, he captured a ship of immense value. He was once caught and he escaped. He purchased a ship from fellow pirate Lolonois (Roronoa inspiration).
Rock was very atrocious. He would threaten to shoot anyone who did not drink with him. He roasted alive two spanish farmers after they refused to hand over their pigs ( reminds me of Kaido boiling Kozuki Oden when he refused to give information, Kaido is a former member of the Rocks Pirates).
Now we come to the interesting point. After 1671, Rock was never seen or heard from again. He disappeared. His body was never found. Even to this date, nobody knows what became of Rock. His first mate became a captain. There has always been a debate between these 3 facts:
1- Rock and his men were lost at sea in a brutal storm.
2- Rock was secretly captured.
3- Rock chose to hide and live the rest of his life in anonymity.
Does this third point ring a bell? For me, yes it does.
“I’ll introduce one of the legends which lurks in ONE PIECE World. ” – Eiichiro Oda at Jump Festa
So I strongly believe that the Lurking Legend is the captain of Rocks, who has been hiding for more than 40 years. Oda used the verb “to introduce”, which means the character he talked about had never appeared in One Piece manga before.
The certain pirate Shanks wants to talk about is Rock. Shanks came all the way to Mary Geoise to talk in person to the world’s Highest Authority. It’s a very serious matter. The last time Shanks warned from some pirate, Marineford War happened. I highly doubt he came all the way to talk about Blackbeard again. Oda wouldn’t make him such a boring character who’s only there to warn people from Teach. Moreover, don’t you think that Shanks is powerful enough to stop Teach by himself without talking to the Gorosei about him?
In Roger’s era, it took three legendary pirate crews to rule the seas: Roger, Whitebeard, and Shiki. Rocks Pirates reigned all alone in their age. When Rock appears again, the whole world will be in danger. That’s why Shanks chose to warn the Gorosei themselves this time. It’s a serious threat. This time, not even Shanks can stop him. Rock started moving, and Shanks probably has information about him being still alive and planning to recreate the crew. Just think about it. He didn’t choose to talk to an Admiral or the Fleet Admiral, but to the Gorosei!
*Theory by Admiral Ryokugyu