The mane 6 just finished off the changelings on a second round when they came back. They thought they were done until a portal out of nowhere shows up near them letting out 6 ponies opposite from the mane 6. The girls must fight for the sake of Equestria to prevent any havoc all around the land.
I would like to thank Cody Cho for letting me use his idea for the Pain 6. I thought it would be a good idea to make a Fan Fiction out of it and Cody approved it. Thank you Cody Cho.