Long, long before Equestria, ponies in that land lived in a number of smaller kingdoms. Princess Essenta, the first daughter of the Dale, sets out to prove herself when her father, the king, sends her on a poorly conceived "suicide mission".
A nosy bookworm, a put-upon carrot, a neurotic apple, a giggly airhead, and a pegasus who's all wind and no thunder. Put 'em together and what have you got? No idea, but Twilight's about to find out the hard way.