The Elder (Book 4: The Guardian Series):

Clare has been possessed by the most powerful angel to walk the earth. Her body is his to use to kill, maim, and destroy, and they do plenty of all three. Together, they set the world on fire. Clare must depend on Daniel to stop them from destroying everything, only she and her angel are unstoppable, and Daniel is the biggest target of all. The war has turned complicated, but Clare knows above all else that she must trust in Daniel or risk losing the light left within her forever. 'The Elde...