User blog comment:Skitzo1/Anyone else hoping for a Unohana flashback to see her bankai?/@comment-3143776-20130612233803

To me, and this is just speculation, I thought of her Bankai as an uber bloodlust-like ability. Completely numbing any and all pain in the flesh (which is why they turned to bone) and just heightens their want to kill. It can be very dangerous because if you can't feel pain, you may not have known your arm was just chopped off. In this situation, I think it benefited Zaraki more than Unohana.