Similar to the ever so frightening Halloween, Friday the 13th brings the supernatural power of the devastating Curse of the Muertos Moon, which turns every pirate on land or in caves undead. Buccaneers, Shipmates, and even Guildmates turn on each other in a massive fight, induced by the Curse and under the spell of the vicious Jolly Roger.
As we all know, Friday the 13th is a day full of evil or bad luck, it also gives Jolly Roger the power to summon this curse on the Caribbean.
In any month, where there is a Friday the 13th, the Curse of Muertos Moon can occur any time it is night in-game. Since in-game time is sped up, this means the event can occur several times during that 24 hour time period. Just like Halloween, once the Curse starts any pirate outside on a main island will become Undead.
While Undead, pirates are able to attack each other - just as in PvP. Once a pirate is 'killed' they wake up in the nearest jail as normal human once again and can still attack or be attacked by those who remain undead - until all the Undead pirates have been killed. During this event you can't board ships, teleport, or go inside any houses or shops. The Pirate Code doesn't apply to Undead pirates.