This is his true form. =3
He's half normal pony, thus the more normal wings & horn and cutie mark.
His cutie mark is fail, but it's supposed to be a strand of DNA.
He has the ability to love, but can't understand it. So he feeds off of it as well, trying to get a better understanding.

(Summary of Story)
His mother, Queen Chrysalis, died. He decides to do what his mother wanted to do in life: Take Canterlot. But then, he finds a small island. He watches the inhabitants. While there are only 12 ponies there that live together, he found more love than even Canterlot could have. Even more to his glee, he finds the source of most of it: A pony called "Anne." Anne was going to marry Gareth. Prince M. Masquerades as Gareth to get what he wants: all the love she has. (Gareth shown here-http://www.furaffinity.net/view/804...../#cid:56096320)