Fairytail : Advent Of Goddesses

A young girl named Sai Latha joined the Fairytail Guild and becomes one of them.
As the newest member she is treated with lots of love and crazyness by other members.
But she goes on a Quest of defeating a monster with her ally Natsu. They soon enough other members discover that their life is in danger and turn on to rescue. They face monsters and villains but not that matters, when their enemies are the Goddesses.

Their power surpasses even the range of dragons and they bind the very formation of everything. What's their mission and why they want?