Pirate Invasion



The Pirate Invasion is a Hardmode event where Pirate enemies spawn and swarm the world's original spawn point. A Pirate Invasion can occur randomly after certain conditions are met, or alternatively, when the player uses a Pirate Map.

For a single-player invasion, the player must kill 120 Pirates before the event is completed. This number increases with each additional player.

Defeating your first Pirate Invasion unlocks the Pirate NPC.

Criteria
The criteria for a random Pirate Invasion to occur is as follows:
 * No other events are currently in progress.
 * The Wall of Flesh must have been defeated.
 * At least one Altar must be destroyed.
 * The player must have at least 200 life capacity (if the player doesn't meet this requirement, the Pirate Map will not work).

Chances

 * First, the Goblin Army event must fail to occur (59/60 chance).
 * If a Pirate Invasion has not yet occurred on a given day, there is a 1/30 chance the first one will occur.
 * If a Pirate Invasion already occurred on a given day, there is a 1/50 chance that another will occur on the same day.

The final probability is 3.27% each morning for the first invasion, and 1.96% for subsequent invasions. On average, a random invasion occurs about every 20 hours and 20 minutes of playing Terraria.

If another invasion is in progress, there is no chance of a Pirate Invasion until the other ends.

Initial event
When a Pirate Invasion spawns or is summoned using a Pirate Map, a message will appear saying that "Pirates are approaching from the (East/West)!"

The message will repeat several times until the Pirates reach the initial spawn of the world or any area of the world above the surface which has a nearby NPC. When the Pirates' initial wave reaches the spawn, their arrival is announced with "The Pirates have arrived!"

Tips

 * Pirates are essentially a harder version of the Goblin Army. Many of the same tactics and preparations will still prove effective.
 * If fought while using a Flask of Gold, one can average between per event, thus making this one of the easiest ways to make money.
 * Pirate Invasions can be used to farm Biome Keys if you arrange for the Pirates to fight you in the corresponding biome. One way to do so is to set up an artificial biome near the spawn point. The other is to simply go near your spawn point to trigger the invasion, then fly to an existing biome that has been prepared to handle an invasion.
 * Pirates themselves can drop Pirate Maps if fought within the Ocean biome.
 * Goblin Battle Standards can be used to farm Pirate Maps if the Goblins are fought within an Ocean biome.

Trivia

 * The Pirates are some of the only human enemies in Terraria.