Six humans are transported to Equestria during it's time of need. (This story is in desperate need of better cover art)
For some, it's to be paid. That is the case of Slade Wilson. With Equestria's large supply of gold and minerals, surely this will be a bounty worthy of a king. With the promise of a reward, he will not hesitate to claim it.
To the one called Steve Rogers, it is for what is right. The price of freedom was always high, but it was always something he was willing to pay, no matter whose freedom it is. He is in it for anything but himself. But perhaps... perhaps this little thing he was promised may be beneficial to everyone he knows.
James Raynor, too fights for freedom. As a bonus, he got to fight for someone else's wellbeing too now. And once this is all done and over with, he'll have more than enough funds and new methods to fight the oppressive dominion.
To the human called Medic. Not only is here for the money, but for the sake of self betterment and SCIENCE. Who knows what magic could do for his research? (And hey, he wouldn't need to cut any unfortunate soul up in the process... that isn't to say he wouldn't want to though...)
To the one called Sanya V. Litvyak it's just so she can be with her parents again. Nothing more.
And lastly, to the boy called Armin Arlert, it's for a safer, a better way to fight and defend against the monsters that are ravaging his homeland.