First, build a Baby Red Dragon, facing up, on the magma vent farthest left. Build a Lava Lobber and a Super Mana Crystal on the magma vents at top right, starting with the right-most spots. Then alternate between building Super Magma Crystals and Baby Red Dragons on the remaining vents, focusing the Dragons on lanes that the Heroes will walk through.
Start a Fire Blast (facing left) from the middle of the blocked Lookers and Jelly cubes. Repeat when available. The point of this is to destroy that Living Wall to free the Lookers and Cubes.
Drop a Living Wall in the middle of the 5th column from the right to block that path; and put a Slime in front of this wall. keep building Mana Crystals in the open spaces at the right edge. Any time the Lava Lobber is recharged, build one over the most protected magma vent.
Keep building Mana Crystals at the left end of the map to distract Wizards and Epic Wizards. Drop Slimes and Skeletons here too, to kill them.
Finally, just keep trying.