Like the theories of Carmel and Big Mom. Hmmm.
I've seen people suggest Xebec has possessed Blackbeard, a split personality scenario. It could explain a lot, including why Blackbeard was so desperate to join WB as a kid.
Blackbeard killing WB and Thatch, taking Ace down etc, it's all getting far more personal than it seemed originally. I suspected he had deeply personal motives but I had no idea what they were yet.
Blackbeard is a fascinating bastard. Very unpredictable. He really is Luffy's foil of thats the right word or well dark/evil parallel or counterpart?