I literally just three starred it! I used mana, triballista, lightning tower, slime, pack rat, that hypnosis eye thing, lightning strike, and bomb. It took me a long time to figure this one out as well.

I started off by putting a triballista on the top of the first section behind the first rock barricade then lightning towers on the bottom also behind the rock barricade. I also did this behind the second set of rock barricades.

I lined the back wall blocking off the treasure room with mana. I let my mana build up and kept replacing the LT's and triballistas whenever possible. After I had my first section set with traps, I added a hypnotist eye thing.

I set off bombs on epics and saved the lightning blast until the second to last wave. As the last wave came, I used slime and a bomb and the lightning towers just did the rest. Good luck! It took me a while to get the timing right.