Implement Robert II Phase 5, Tonic retaliation

Phase 5 is an optional phase for the final boss, only reached if he ends
up using Alcohol and recovering all his health.  Asking the player to
hack off another 7 HP bars while being hammered with Tier-2 magic is a
little too much to ask.  Besides, he's supposed to be emotionally
exhausted at that point, it makes sense he would stop with the fancy
moves.