So the answer was Tyrael:
The original words suggested arthas, save "But frozen I am not", ruling him out. Additionally, it states him a "godsend", both a play on words with him being an angel, and the metaphoric sense of being a boon, while NOT being a villain, which arthas is as Lich King and slayer of Fordragon (Sort of).
As for Tyrael, his sword El'Druin is a part of him, and judges those it touches - it cannot directly harm those that are righteous, which is why...
Posted: Mar 10, 2014