By Entering each Shrine, one character will be allowed to donate money and get a Stat increase in return. You cannot increase a Stat past the character's racial maximum, so don't try. The Shrine of Intelligence is in the northwestern part of Ambrosia. To reach it, Unlock the door northeast of the entrance, then Unlock the door headed back west. Take over the Pirate ship in the nearby water, then sail west to the grassy area. Unlock one final door to reach the shrine.