It may seem late for this post, what with the month two-thirds gone already, but rest assured, mateys, the May 2014 Seal o' Piracy is easy to snag. All it takes to get one of these limited edition trophies for your very own is...
Engaging in melees with 3 Brigand Kings. (Cursed Isles and Brigand King Blockades not included; credit is awarded for reaching the melee, whether you win or lose.)
To reiterate, that's "engaging in melees with," not "defeating." Win or lose, your encounter with Azarbad the Great or Gretchen Goldfang will count toward your seal just so long as you reach the swordfight or rumble stage of the game.
So that's your first lucky break. Your second is this: You can all but buy your way into that encounter.
That's right! Just visit the Explorers' Hall nearest you and, for roughly 1,000-4,000 pieces of eight, purchase a Brigand King Compass. This item, when placed upon the navigation table, will lead you straight toward the particular Brigand King to which it is attuned. And though you do have to be an officer to sail a ship into this deadly embrace with destiny, you don't have to be an officer to buy a compass. An enterprising pirate might consider buying a compass and offering it to the next officer whose pillage he or she jobs for.
It's also possible to encounter a Brigand King Compass inside of a Black Box. Black Box Series Five has just recently become available, being announced on May 1. For 10,000 pieces of eight, you can purchase one of these mysterious containers... and see what's inside! You'd be buying it for a chance at one of the more exciting rarities--rogue class ship designs, black pets, black chromas, black sea turtles, and the ever-coveted black raven familiar. But should fortune not favor you thuswise, a compass makes a satisfying consolation prize.
If you don't want to spend money up front, clear some time in your schedule and prepare to go a-pillage! Brigand King sightings are one of the expeditions that your crew might extort from a defeated brigand or barbarian at sea. Your odds are relatively high. Your Examiner set sail with Serenidad upon the Opal Ocean the other day, her navigation table already primed with a Brigand King compass; several battles down the road she had already happened upon two more Brigand Kings and achieved her Seal o' Piracy.
It's interesting to note that while Brigand King Compasses tend to lead daring pirates to Brigand Kings of great difficulty--say, a fully-staffed dhow when you're solo on a sloop--Brigand King Sightings extorted via pillage often result in a more evenhanded battle.
Good luck and happy hunting to you!