Board Thread:General Discussion/@comment-26391241-20150511234157/@comment-24674051-20150513142829

Also, while it was never made clear, I think that when Zoso convinced/tricked rumple into killing him, he was similarly at the point where his heart was almost black, and knew it. so he willingly sacrificed what little was left of his life in order to insure that the Darkness was kept in check. My guess is that all Dark Ones reach that point. In fact, Rumple was at that point, but he was too much of a coward to even offer his life, and I think may just be fortunate that the Apprentice was available and willing to help with his problem.