at the last lv, you killed the tower "wow, i thought it would be harder than that!" and then all of a sudden all your strong units start dieing by "the end" and when you're about to win, 7000 life points left and the boss has 5000 left, your angel dies, and at the end, you win, but sooo close, you would die.
(by the end, you should have everything upgraded) you should do Mas Meragin's way and then start maxing out your mana to 9999, then you should start summoning angels and dragons,(stop the arrows when you start spawning). when you kill the tower, start pressing 1 it is the key for hobbits, although they dont do anything, they hold back the boss, you dont even waste a bit of mana! start spawning angels, at the end when you still didnt kill it and its close to your tower, start the arrows again and start summoning dragons in case your angel dies and the other angel is too slow or your running out of mana.
dont stop summoning hobbits, Hope this helps!