Probably just killing Sabo and having the fruit reborn.
It is implied here that he can take the fruit right there and then.
Probably Blackbeard told his entire crew how to extract fruits from dead people.
The titanic captains are always spread out on missions, Blackbeard cant be with them all to get them fruits.
They know how to do it on their own.
@HellBlazer04
don't think I can get on board with this speculation. Oda most likely keep the multiple fruits ability strictly reserved for Teach. Don't think Shiryu's sword getting a DF will be an exception here
Certainly, a speculation for now but as I said, often their opponent share something in common.
If DF doesn't happen with Shiryu's sword, the whole point of that ability was for Mr4 and Spandam which is kind of a wasted potential.
What DF is it supposed to be though. Shiryu pre DF was as dangerous as Magellan, indicating his high skill with the sword, allowing him to be incredibly lethal. A blade being transformed into another object wouldn't really add up to his strength. So it's more likely to be a paramecia that adds features to his already existing power.
But then again, being as dangerous as Magellan before his DF, on top of having an awakened invisibility fruit and maybe an ACoC upgrade should be tricky enough. King's role was to have Zoro overpower the invulnerable, while Shiryu will give Zoro the opportunity to target the undetectable.
You have to think of it like this - what ability would give Zoro the most trouble - Shiryu's Ittoryu is way too simple for Zoro to struggle against it. He doesn't have powerful haki to compete with Zoro that way, as Shanks/Mihawk can, that's why he needs to compete in a different way.
The most trouble Zoro ever had was against Kaku's Yontoryu and since nobody in post-TS has had an overwhelming combat style, I think Shiryu will be the one with it. Transforming the sword into an object is not to add up strength, it is to pressure Zoro where he is the best at - combat style. Paramecia is out of the question because only Zoans can be fed to objects.
I doubt he has CoC let alone aCoC. Plenty of Zoro's obstacles have aCoC, no need for it on Shiryu.
King was a test of raw strength and cutting power. Shiryu will be a test of combat style and cutting formless Nothingness.
Only one DF comes to mind and we already saw it - Orochi's fruit that was portrayed as Power once handed over to Orochi.
Coincidentally, it turns Shiryu's 1-sword style into an overwhelming 8-sword style and that is what will give Zoro trouble, needing Asura.
Also, Orochi has literally shown off nothing of the fruit, even less than Absalom did with Suke no Mi.
Heck, if Oda wants, Shiryu could complete Blackbeard's theme of all 3 types if he obtains Kizaru's sword of the gathering heavens.
Coincidentally, Kizaru is showing off the bare minimum despite several combat encounters...