Wisdom Gems are one of three spirit gems found in Phantom Hourglass. Link uses this gem in order to channel more power from the Spirit of Wisdom. They are scattered all across the World of the Ocean King, and Link can find a maximum of 20 Wisdom Gems. Upgrading Neri at 10 Wisdom Gems is the equivalent of acquiring Blue Mail--it reduces Link's damage by half. Upgrading at 20 gems reduces his damage to one quarter like Red Mail would in older titles. Also, if Link has a shield, it allows him to stun weaker enemies if they run into it.