Avast, ye scurvy dogs!
Blizzard are offering a special flying pirate ship, The Dreadwake, as part of a limited-time promotion.
Purchase 180 days of game time from their Shop and receive The Dreadwake as part of the bundle. In addition, if you've purchased game time recently, or are on a 6-month recurring subscription, you may already be eligible! Check the gifts tab on your Blizzard client. Also, if you can't afford it this year, don't panic: Blizzard have announced that The Dreadwake is going to become a regular Shop item some time in 2019. See their Promotion page for more information.