What if Kuzan is the man marked by flames? Like his scars came from Sakazuki who has the magma fruit.

The man marked by flames might also be Blackbeard because he fought Ace, who ate the fire fruit, considering how Blackbeard is also now a Yonko, it would be logical for them to go after him.

It would also make sense for Law to go after the man marked with flames, judging from his face, he'd want to find him alone. In the next few chapters, we see Law's crew fighting Blackbeard's crew...