That's either pure brilliance or plain stupid. Till now the strawhat was solely a symbolic object, it didn't have any particular importance outside that, but now it somehow connected to the dark past of the WG. The national treasure of the Celestial Dragons is an oversized strawhat located deep below Mary Geoise in a huge vault with freezing temperatures

Talking about being surrealistic.
Now the shadowy figure seems to be wearing something that's awfully reminiscent of a crown. So my best guess would be that one of the royals used the Reverie as an opportunity to infiltrate Mary Geoise or that someone is impersonating a royal for this specific purpose. The fact the he needs a wanted poster as a reference point, seems to indicate he was knowledgable, but not familiar about what he was expecting to find. Possibly a member of the RA? Intriguing detail he had more than one wanted poster.
And Charos definitely is going to get his face punched again, probably by Sabo, but
maybe Dragon if Oda wants to underline the father-son relationship.