Blackheart is a small, quick, and oddly powerful pony. He does not use magic too much, and hates almost everyone.
Blackheart's original name was Smallfry. He was teased by all sorts of ponies as a filly. Not much is known on how he got his cutie mark, but people say when he got it that it was horrifying. When Bloodstripes wants to make another planet to overthrow the moon, Blackheart helps him. Blackheart sees all the power Bloodstripes has an turns him into stone. Later on that day, Blackheart is seen dead next to a strange shadowy pony. The filly who teased him (who were now all grown) remember him as Smallfry and how innocent he was.
Blackheart is careless. He also seems to show a hatred towards everyone. Blackheart left his young child because he didn't want him, showing that he has no feelings for anyone. As a filly he was innocent and always wanted to have a cutie mark before anyone, sadly this didn't happen. Discord even states that Blackheart was a pony with no sense of humor.
-Bloodstripes might be one of the filly who teased him.
-Blackheart and Bloodstripe are both evil pony who don't have wings.