The Greater Black Sea Battle, not to be mistaken with The Black Sea Battle. A much smaller battle in which ended with no victor.
Diggers Johansen was captured by the Skeleton Crew. Because of this, Admiral Blue Beard wanted to save him, but Lockpit Cabot had a better idea. If the Privateers formed an alliance with the Sea Marauders, they could use their vault of transformation to disguise one of the Privateers into a Skeleton to make it easier to free Johanson.
The alliance formed, they searched for the Phantom. Once they found it, Dagger Tremean was transformed into a Skeleton, ready to free Johansen. Once he saw Johansen, he explained to him about the Skull Staff. The Skull Staff was the only thing that gave the Phantom it's invincibility. But if they got their hands on the staff and freed the Lost Souls, who gave the invincibility, the ship would only be as powerful as any other. They freed the Lost Souls, then escaped together, and strait away, the Stormstalker and the Avenger started attacking the Phantom, causing it to sink. The two sides, believing to of defeated the Phantom for good, rejoiced until the night.
One day, the Skeletons found an alternative way to get their ship back, by finding the Madillian Staff. Then, the Phantom was resurrected. Meanwhile, reinforcements had come for the Privateers. It was then that they thought that they no longer needed the Sea Marauders, so they broke the alliance.