Board Thread:Questions and Answers/@comment-24919788-20140509022515/@comment-8986886-20140513214255

Schiffy wrote: What we do know is that during her fight with Zaraki, she kept "killing and healing him" over and over again. From this, is that the Bankai possibly has the ability to resurrect (perhaps only on things that have . It's ability to kill was, most likely, just from the fact that it still is a blade with a sharp edge. Those hurt people. They also kill. My guess is that the ability to heal (probably upon stabbing) is completely controlled, meaning that she can resurrect with it when she wants to, and use it as a normal instrument of stabbing when she doesn't.

Before she activated her Bankai, though, Unohana managed to fatally wound Zaraki several times, causing him to lose consciousness. Even then, she was able to revive Zaraki after she had stabbed him, and she only released her Bankai, when he had become strong enough to severely injure her.

When Unohana stated that it was time to get serious, I doubt she was talking about a more potent resurrection; I believe she just wanted to maximise her Reiatsu at the time. That said, her Bankai should have some sort of healing properties, that much we can agree on. ^^