In today's game, I've chosen a good starting formation with Shattered Mirror and Gloom Owl, Amped Zapper, and Gloom Owl. I chose them because they are powerful and have a lot of attack, and I'm going to face powerful enemies like the ones you'll see below.
In terms of spells, I've used Buildmaster and Cheapo in order to take advantage of their savings on mana. The problem at this level is that there isn't much mana, so you have to start with a strong tower and use these spell sales to kill as many demons as you can before you can get some mana from them.
I tested on card at a battle and it was Shattered Mirror to see what it can do against fiends with its high physical damage and I also test spells with them, I put Shattered Mirror close to fiends opening using cheapo and the remaining mana, I have used buildmaster to upgrade it and in the first wave it did amazing work killing all fiends except some flying ones but as I have said it is alone will not work as low mana gained from first wave and the second one is massive so I have to put them all and gives up on Upgrades.
As you can see, SLAYING MANTIS will not have fun with you because it has hit points of 3500 and is so slow. This is the only thing you can do to stop it, as well as CAULDRON DWELLER, which has strong armor and more than 600 hit points.
The challenge in this level will be these two fiends, who are so strong. SLAYING MANTIS
A chitinous mistress of rot and rancidness, can give birth to Terror Mites by the bucketfull.
3500 Damage Points Speed of fifty Every two seconds, four Terror Mites are born. CAULDRON DWELLER
The most beloved kitchenware of the witch has come to life and is eager to spit its bile on you. Iron armor that protects you from physical harm. 650 Damage Points