Before this Enbu start, Jellal told Fairy Tail that he can feel some unknown magic power in this Ebnu for many times. So in order to find the answer of this secret, Fairy Tail decided to join in
and Jellal also make up as Misutogan to help them.
A few chapters ago, we know that the king of this country can control the compitors of this game, it means he can choice the two he like to fight. And the knight of the king seems is one of the programmer of the secret magic power, At first I thought he want the power of Dragon Slayers and grap Wendy to get that power, but I was wrong. We can infer something from now on, they want to use the magic of someone like Lucy. It's just like some magic type to the whole universal or anyther space.
I believe when Elfman win the game, its the turn point of Fairy Tail in the Enbu, even though there are still have some strong team, but Team A and B will overcome all of the things finally. So this is Fairy Tail!