Board Thread:Game Discussion/@comment-4682625-20130806011111/@comment-76.248.30.211-20130806043712

Yes, all of your knights and your friends knights will be rejuvenated, but you can only do this when prompted so make sure you have enough crystals/energy going into battle. Same thing happens when you want to extend a Boss battle in any of the areas on the map, though it costs less than it does against the Epic Boss.