Ok.. here's how I finally did it. Use the frost sword and freeze him so you can move and heal. Then h it him with the death thing. It's the freezing part that is the only thing that will let you survive long enough to kill him. I was at level 19 because it took me so long to figure it out lol!
 "Hands of War"){kind=icon}
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 "Bloons Tower Defense 3"){kind=icon}