Well there isn't a trick to beat the level but you can play older levels and collect itens to make your heroes stronger... This for sure will gonna help you.
To beat any level i see 2 kind of tatics...
Just at the beggining of a level create many heroes as possible and dig the path to the enemies buildings and start the attack and keep it until everything is dead. Remember the enemy buildins get stronger as the time pass, attacking then in the very beggining of the level you gonna pick them in their weakest phase.
The other tatic is build your dungeon, collect all crystals and build all possible unit constructions them when the dungeon is done and you don't have any more crystal to spend start the attack.
Hope this helps and good luck trying to beat the level ^_^.
