Awakening of Evil

I honestly couldn't complete the final stage in the third mission – the devil has an advantage in initiative, number of troops, attack power, and superior defense. You can only control imps until they die; otherwise, they drain all your mana, and if you control them, they immediately open a portal, and that's it. I didn't get a Berserker, and I didn't get the magic staff. In the fifth mission, in the battle with the devil, his 900 dogs will easily defeat 300 black dragons. You can be saved by a magic staff with the control spell and dark riders and assassins, but it's easier than the third mission. In it (the fifth), I didn't complete any quests except for retrieving the Grail. I killed all the zombies, but I didn't collect the reward; I somehow got lost.