Gaia is a recurring character in the Mana series. He is the guardian of earth. He is in many regards similar to Treant the guardian of nature who he is linked to in one way or another in most games.
In Secret of ManaEdit
There is a location called "Gaia's Navel", which might be an retroactive reference to him.
In Sword of ManaEdit
In Children of ManaEdit
Gaia and Treant appear to the player in order to assist them against the Mana Lord. Both of them were also involved in the events ten years ago, but disappeared afterwards and were not seen till the events of Children of Mana.
In Heroes of ManaEdit
Crystallized forms of Gaia's power, Gaia Stones, are found all over the world. They are one of the two resources needed to build and summon units, the other one being Treant berries.