Heart of the Night

I tried several times with the main hero, but I couldn't beat it. I played without any losses, but the elf died. Then, a hero appeared with a large group of undead with decent stats. I thought I could defend the castle, but no luck. The catapult destroyed the gates and the tower in three shots, and the ballista took out the archers, and that was it. I guess it's not meant to be. As they say, "some hats are too big for some heads."