Every. Single. Step of the journey, these two mirror and influence one another. Even now that we’ve entered the New World, what’s they’re doing is directly opposed – Blackbeard is stealing the fruits of the old generation of pirates, bringing their powers together, while Luffy is uniting the next generation of pirates, bringing their powers together.
So now the question is – what does this mean going forward?
Well, if Blackbeard is Luffy’s direct contender for the title of Pirate King, Blackbeard needs to reach Laugh Tale. The only way to do this is to obtain the Road Poneglyphs, decipher them, and sail in the direction they point. So we know this is likely to be Blackbeard’s next objective. We also know that one’s journey affects the other, and what has Luffy done recently? Ransacked Totto Land and forced Big Mom to chase him to Wano. This has created a power vacuum in Totto Land that Blackbeard can take advantage of; especially since the Big Mom Pirates left behind are already weakened due to Luffy’s actions.
Now, Blackbeard attacking Whole Cake Island for the Poneglyph isn’t a new theory, but what I’m betting is that he’ll leave with something more – after his assault, Blackbeard will obtain both Big Mom’s Road Poneglyph and kidnap Pudding. Here’s my reasoning: Luffy and Blackbeard’s journey is mirrored, as I’ve hopefully aptly demonstrated. This means that if Luffy does something that advances him towards being Pirate King, Blackbeard will take the same step albeit in an opposed manner. So, since Luffy snuck into Totto Land in order to rescue a crew mate, Blackbeard will subsequently attack Totto Land in order to kidnap someone in return. This will be Pudding.
Why Pudding? Well, as far as we know, there’s only two ways to read the Poneglyphs, you either decypher their texts or you somehow utilize the Voice of all Things and learn their secrets that way. Since Nico Robin is the only known living character who can read the texts, that forces Blackbeard to utilize the Voice of all Things. But, everything we know about Blackbeard indicates that he doesn’t have this ability and he most likely never will. Remember, he’s opposed to Luffy and since Luffy will decipher the Poneglyph through his friendship with Robin, Blackbeard will in turn force someone to decipher them for him.
Coincidentally, Pudding was specifically conceived by Big Mom because it is believed that members of the three-eyed race have the potential to unlock the ability to hear the Voice of all Things. While she herself has said that she doesn’t yet possess this ability, I believe that her development during Whole Cake Island will bring her to a point where she will unlock it. Blackbeard, knowing this connection, will take advantage of it and force Pudding to decipher the Poneglyphs for him, thus continuing his mirrored journey with Luffy and bringing him one step closer to becoming a contender for Pirate King.
*Theory by Therrester
