With so many powerful characters from the new generation on the seas, it was only a matter of time before they clashed against one another. As soon as Luffy, Law, and Kid left Wano, they became enemies and set out to fight against each other and the remaining members of the Worst Generation for the title of the Pirate King.
As seen in One Piece Chapter 1063, Oda has set up a massive fight between one of the members of the Worst Generation Trafalgar D. Water Law and Yonko Blackbeard. With this clash, Blackbeard will have a chance to obtain information about Ancient Weapon from Law.
At the end of Wano we learned that Pluton is actually hidden beneath the island, and Law and Robin got to venture below for the info. Blackbeard was waiting on the next island to steal the Poneglyph rubbings from whoever showed, but I’m thinking he can get more since he is clashing with Law.
Blackbeard kidnapped Pudding to read the Poneglyphs, but she also has the Memo Memo no Mi. What if he forces Pudding to use her fruit ability to look into Law’s memories? He’ll know where an Ancient Weapon is, and what he needs to do to get to it. (Knocking Wano’s borders down)
But why would Teach look into Law’s memories? He’s smart and loves information. I’m thinking he’d want to see how they defeated Kaido and Big Mom, maybe get some information on Luffy’s new form.
Theory by KingBongBling (https://www.reddit.com/user/KingBongBling)