Help! Trying to find a fantasy movie I've forgotten

There was a fantasy movie that I saw as a kid which I vaguely remember but haven't been able to find the title in years. I was wondering if any of you might know the movie.

Basically, the part I remember most clearly is that the villain was like a black sorcerer with a heart of stone or metal or something hard to destroy. Only with a special sword could the protagonist, a young boy (maybe a teenager), pierce his heart. There's a part after the boy receives the sword from the smith where he cuts the anvil in two.

Also, at the end, I believe he flies away from the evil sorcerer's castle on a pegasus (I think with a girl around his age flying at the back).

That's about all I remember, though I believe the boy also had an older brother he looked up to who died. I think there was a flashback scene in the beginning with golden lighting where his brother was telling him something.

Also, for a movie starring kids, I think it was fairly violent with a beheading or some other violent execution somewhere towards the early part of the movie.