Earth Temple

The Earth Temple is one of the two main temples and the fifth dungeon to be explored in The Wind Waker, located leagues beneath the Great Sea down in the now-sunken land of Hyrule, beneath Headstone Island. After the triumph of the Hero of Time over the Dark Beast Ganon at the end of Ocarina of Time and his subsequent journey back to his own age, it was decided that two new temples (the Earth Temple and the Wind Temple) would be constructed to safeguard the power to repel evil that dwells within the enchanted blade the Master Sword, by means of providing a place for the two new Sages to offer up their prayers to the Golden Goddesses, the prayer song for the Sage of Earth being the Earth God's Lyric. When the Dark Lord Ganondorf somehow escaped from his exile in the tainted Sacred Realm, he returned to Hyrule in a red wrath and found that there was no Hero present to oppose him, causing him to seek a way to deacvtivate the Master Sword. In turn, he ordered the great Poe, Jalhalla, to invade the Earth Temple and murder the then-sitting Sage of Earth, the Zora known as Laruto. After Laruto’s death and the following invasion of Hyrule orchestrated by the Dark Lord, the Golden Goddesses brought down a torrential downpour known as the Great Flood that buried the land of Hyrule beneath a vast ocean that came to be known in time as the Great Sea. The entire kingdom and all still in it (namely Ganondorf and his army) were sealed within an enchanted air chamber that prevented the water from destroying the kingdom, and the entire kingdom was left frozen in time. The water did not leak into the Earth Temple, as its two entrances were safely out of the water's reach. It was here that Laruto’s spirit lingered on, awaiting the time when a new Hero armed with the Master Sword would come with a successor Sage to restore its power and destroy the evil that now haunted the temple. Many centuries later, Link, the Hero of Winds, came to investigate what became of the Sages of the Master Sword and to restore the Master Sword’s power to repel evil. He brought with him Laruto’s predestined successor, a Rito by the name of Medli, who bore the harp once used by Laruto herself, and they worked together to solve the mysteries of the Earth Temple and to purge it of evil. They faced many evil creatures within the temple (defeating a set of Stalfos along the way) and destroyed Jalhalla, freeing Laruto of her obligations and partially restoring the Master Sword’s former power.

History
The purpose of the Earth Temple was to keep Ganondorf imprisoned following the events of The Legend of Zelda: Ocarina of Time. The sages of the temple were Zoras prior to Wind Waker, in which the Rito become the race affiliated with the temple.

Trivia

 * The reason Zoras were sages of the Earth Temple was probably due to its close proximity to Lake Hylia.
 * The Earth and Wind Temples cover the elements not already represented by the temples in Ocarina of Time, though they are more analogous to "shadow-" and "spirit-themed" levels in comparison.