its actually insanely stupid that you're REQUIRED to spend so many gems on one specific mini box, just to get power tool dragon so you can do stage 15, absolutely idiotic who ever made that mission should be fired.
Let her summon her dragon, wall of d her, flame wingman for 2400 effect damage. I got lucky to do this on first try. Take note that it's a specific lvl akiza, I think it was lvl 30. Maybe u just doing the wrong difficulty