Spirit Gems
From Zelda Wiki.org
Spirit Gems are items that are hidden in Phantom Hourglass that can be found by opening chests, solving puzzles, purchasing, checking the mail, or completing a certain event. There are three in total: Power, Wisdom, and Courage, and each has a different effect depending on which Servant Spirit is equipped, and of those there are 20 total gems of each version to collect over the expanse of the World of the Ocean King.
Enhancement and Skill Upgrades
When Link collects 10 of a certain gem version, he sees an ability enhancement on the part of his sword or in his physical skill set, however, upon collecting all 20, Link is upgraded with the full extent of the Servant Spirits' power.
For the Spirit of Power, securing 10 gems ignites Link's sword and doubles its attack power. Getting all 20 quadruples the amount of such power.
For the Spirit of Wisdom, obtaining 10 gems doubles Link's defense. Getting all 20 quadruples the defense ratio.
For the Spirit of Courage, getting 10 gems powers Link's sword with the Sword Beam technique. Getting 20 doubles the width of said beam.
