Din’s Pearl is the first of three pearls that Link has to obtain. This pearl is Prince Komali’s precious possession, as it was given to him by his deceased grandmother. Komali wanted to visit Valoo and get the scale needed to grow his wings; however, Valoo was acting up at the time, making Komali feel upset. Link, with aid from Medli, manages to defeat Gohma and calm Valoo down. Prince Komali feels that giving the pearl to Link would give him courage, and thus decides to give it to Link.Later on, Link places the pearl on Northern Triangle Island to make the Tower of the Gods rise from the Great Sea.
Din’s Pearl has the same mark on it as the symbol for the Tune of Currents from Oracle of Ages and as the Power Gems from Phantom Hourglass. This symbol also appears on a door in the Temple of the Ocean King, but the Spirit of Power is needed to open it. – Zelda Wiki