@Gol D. Roger
Basically what Reborn said.
Irrelevant but interesting: Teach's line in this chapter about DF benefits outweighing the drawbacks combined with the massive pain amplifying weakness of Yami is a big alarm, Teach as someone that read the DF encyclopedia knows something we don't.
Not only Yami is an anomaly amongst all three DF classes by being able to negate them, but also is what Oda used as an example of an invincible power in his early sketches, where he said only the sea can stop it (interesting that Law mention this weakness in this chapter). I'm fully convinced that no matter how crazy Gura or Teach's next Zoan feats are, Yami will still triumph them all. A Nika-like power could very well be sleeping within it.
I totally agree with you
And, hear me out.
We know BB read some df book and was looking for yami for a long time. He even boarded WB ship for this vary purpose for decades (Below panel)
In the above panel he also says - this ability chose me (I will come back to this later)
Yami is hyped as most powerful ability of all df types but why?
The best explanation why yami is powerful comes from following panels
Yami can return everything to nothingness and no one escapes it's gravity - it's perfect black hole - most destructive force in the Universe.
He uses yami to even extract the df spirits from the body of others when they die.
Though, BB can become hammer in sea water but it won't matter if yami can absorb sea water and reduce it to nothing.
Now, let me come back to why BB said "ability chose me" and this is where my headcannon starts
Xebec is really BB - reincarnation or his son.
We know BB ship is named xebec but there is one more thing about it - Xebec in historical context was
3 mast Mediterranean ship - key note here is 3.
And, BB has things going on with 3 - 3 skulls on ship, 3 guns, 3 claws which he used to give shanks 3 scar and possibly 3 dfs