Blue Beard's Avenger (Avenger for short) is a Privateer ship and is owned by Admiral Blue Beard. The Avenger was a ship set but was never released. However, it is on the map that comes with the primary skull sets(shown at right). The name may be a retcon pun of blackbeard's ship Queen Anne's Revenge.
In the story, Blue Beard ordered that they attack Dread Eye's Phantom and get the Letter of Marque, but during the battle, the Privateers ended up overwhelmed. They achieved getting the letter of marque, and they all piled into a dinghy while the Avenger was destroyed. Blue Beard was then killed by Dread Eye.