Pirate Map

The Pirate Map is a Hardmode item used to summon a Pirate Invasion. It has a 1% chance of dropping from any enemy in or close to the ocean during Hardmode.

Farming
Minions are convenient for farming Pirate Maps. If the player has a Neptune's Shell and an item summoning a permanent minion (such as the Pygmy Staff), he/she can simply wait underwater while the minion(s) kill incoming enemies. Items that increase the number and/or damage of minions could make the process safer. Also note that minions can attack enemies outside the map border, meaning the player should stay some distance from it in order to not lose drops.