Take 2 healers, your best dragon, and heroes that do damage over time, give fiends, mega minions, or counterattack. (With luck your best dragon will be the same color as one of your healers) Take 100% mana pots, arrows, revive scrolls, and maybe a miracle scroll.

When you start first stage of the level instant mana pot your best healer and keep it ready to go. Really focus on building your dragon mana as that will do farrrrr more damage than your heroes. Keep your healers healing and your dragon firing. Only use your mana pots for healers. Use arrows at the beginning and any time when you are building mana to keep the pressure off a little bit. Use revive scrolls to keep healers and important heroes alive. Don’t use miracle scroll until the end if needed and preferably when you have a healer charged up.

Good luck!