When I was young (so this was about 30 years ago) I saw this cartoon about a character (I don't even remember if it was a young man or woman) who was sent on a quest. I think he or she had to defeat three magical creatures.
The thing was, a piece of each creature could be used to defeat the next one. If I remember correctly, one had the power of ice, and after he (or she) defeated it, a sliver of its heart(?) was taken and used to defeat the next creature which had the power of fire.
Does anybody recall an animated film with that plot? I'm quite certain it was a Japanese cartoon that was dubbed in English. (It may have been an episode of Prince Sapphire, but I'm not sure.)
(P.S. It seems the plot is a bit like how Perseus had to defeat Medusa who then used the severed head to defeat the Kraken, but I know that cartoon was definitely NOT about Perseus. I don't know why Prince Sapphire comes to mind.)