They are rewards for completing each island of the main quest - only 5 have been unlocked so far. Each has a different passive bonus and you can have up to 5 active at once (you need to tap them to activate them).
1) 10% increase in earned Rank points (character level) 2) 5% increase in Enhancing xp 3) 2% increase chance in getting Super Enhance 4) 5% increase in earned EXP (job level) 5) 5% increase in rupies from quests
Not sure if any of the mods still support this community, but they should be aware that the forums are infested with bots and that their forum needs to be upgraded.