Finally beat the iron challenge on The Dark Tower. This is how I started out:
I've found that to be the easiest way to complete the challenge. Barracks are pretty useless, played several matches beforehand with them and enemies would always make it passed them. But this way they're under constant assault. I upgraded most of the archer towers to rangers and split the mage towers between arcane wizards and sorcerer mages. Sorcerer mages because those rock guardians help slow down the enemies.
