The Needs Of The Many

I've always wanted to visit Equestria (what brony hasn't), but I soon discover that things very rarely happen the way you intend for them to when I suddenly wind up there myself. The ponies all live in a constant state of fear as a dark gloom lingers over the land, many of them suffering from life-threatening afflictions. Not only that, but I find myself with strange new abilities.
What has happened here? What's happening to me? I will soon discover that I play a major part in the survival of the pony race, but am I up for the challenge that faces me?

(the cover of the story does not reprisent the story)