Board Thread:General Discussion/@comment-25536775-20170510235618/@comment-1916997-20170523145530

I would say that since Black invented the Dark Curse in the first place, she was able to make a version where she didn't need to crush a heart. Besides, it is clearly somewhat different, as the smoke was different from what we have seen everytime the Dark Curse is cast. So long story, short: It's not the exact same curse, so it doesn't need a heart.