A word about Krag. I would call him one of the strongest heroes in the game. His ability is also overpowered and useful. Level up his attack and ogre skills. Then, Devil's Might, Darkness, Cursed Ground, and Ogre Strike. After that, Luck and Chaos Ward so they attack with fire. You'll see the result yourself. Also, find him a weapon with 30% attack speed, plus support troops. He'll take out 3-5 angels per turn, plus support troops (it's better to put ogres on support).