NOT GOING TO HAPPEN. And stop complaining about the difficulty, they need to buff the opponent because he isn't a real person and it would be too easy if he followed by the same rules.
SilverBladeTH, I salute you. You realize that you shouldn't rate low for something you don't understand. So I will help you rate this game higher. You need to go onto the "equip" screen (bottom center). Now click on one of the starter unit cards you were given. Move it up until your mouse/arrow is pointing at the center of the black rectangle under "Unit cards." It should now be equipped. I dunno if I helped, it might be a bug you are facing, but try it.
Oh, I tried doing the hero's health, but I can only heal him, I can't freeze his hp, so he is not invincible. I can make a super enemy, which is pretty fun to make then try to kill with like a hundred of the fire demons.
Okay, honestly people, if you are free to ask questions you should at least TRY to answer them yourself. People have been posting strategies on how to beat the cave of trials for 800+ pages now. LOOK.
Alright, a useless update on stuff I have been able to change. My castle's health, the enemy castle's health, experience, gold, mana, exp and gold gained in battle, turn phase, number of times I have beaten the game, and the cooldown times of 1 ally unit and 1 skill per game (as well as passing the cap on the number of units you are supposed to have at once). If anyone wants to know more just ask.