I think this movie could be a big hit, honestly, and can see it going in a couple ways.
1.) and most likely; the film is an adaptation of the Athena's Fortune novel. I think this is most likely because the story itself sets up lore for both how Ramsey/the Pirate Lord discovered and chartered the Sea of Thieves, but also how Larinna made her way to it as well. The tales that interweave on a chapter-by-chapter basis work nicely, and would fit as a film nicely I think.
I even came up with some fan-castings of the characters, though you'll notice there are many Black Sails cast members (that show is so peak):
Crew of the Magpieâs Wing
-
Ramsey: Mark Ryan or Toby Stephens. Both from Black Sails as Gates and Cpt. Flint - Toby also narrates the Athenaâs Fortune Novel and would kill it again.
-
Rathbone: Ralph Fiennes
-
Shan - Mads Mikkelsen
-
Mercia - Penelope Cruz or Michelle Rodriguez
Crew of the Unforgiven
Supporting characters/villains
-
Gideon Graymarrow: Zach McGowan
-
Eli Slate: Toby Stephens (I know lol, heâd be good in either main or supporting or Steven John Ward (Mihawk from Netflix One Piece)
-
Briggsy: Jessica Parker Kennedy
-
Sticher Jim: Anton Lesser
-
Kraken (voice): Jack Black (haha)'
Conversely, they could go the route of an entirely new story, in a brand new character's eyes, as they make their way to the Sea of Thieves and go on an adventure of their own. Admittedly I am more hopeful of the first option.