In the beginning, there were the 4 races, ponies, the divines, and the Jall, and another.

Ponies represented water, as they flowed freely throughout the lands and gathered all in their comforting embrace.

The divines represented air, as they were above the other three beings, and kept balance throughout the world.

The Jall represented fire, as they wished nothing more than to consume the world in their rampage.

Another race, long forgotten by time and distance, represented earth, as they grew stronger under pressure, and even when they had nothing supporting them, they would persist. Therefore, the element earth came to represent a bonding of life, greatness, and evil, as its people were a race that ran on ambition, potential, and persistence. A type of being that would stand strong in the face of any opposition for any gain, and would never truly fall until complete destruction.

Now, Celestia, Luna, Twilight, Cadance, and Discord have been forced to call upon the earth beings to help defend Equestria from the legions of evil, and boy did they get some really great beings from earth.

Because Earth is the domain of the humans.

*rated for epics and profanity, starts off after the Season 4 premiere but before Castle Mane-ia*