Pirate's Charm

The Pirate's Charm is a stone necklace given to Link by Tetra in.

Uses
The Pirate's Charm allows Tetra (and the King of Red Lions) to communicate hints to Link. Tetra can see what Link is doing through it, and he can hear her voice. It gives off a sparkling blue glow capable of altering the lighting of the immediate area when Link examines it. When someone is trying to reach Link, it alerts him by chiming. It is used mostly during the start of the game in the Forsaken Fortress.

According to Daphnes Nohansen Hyrule, the Pirate's Charm is an enhanced version of the then ancient Gossip Stones, which appear in and, that he himself crafted. It was subsequently passed down through the Royal Family until it was inherited by Tetra, who is indeed Princess Zelda. The method of its creation is never divulged.

Trivia

 * The charm's description in the Quest Status subscreen implies that it's function is to allow Link to speak with Tetra. Despite this, after Link is tossed from the Forsaken Fortress by the Helmaroc King, she only contacts him once more throughout the remainder of the game, after he is caught stealing Bombs from the pirate ship. The majority of its use is instead by the King of Red Lions.