I beat cave 5 using goblins, dragon riders, succubus, witches, dwarves, and centaurs. For spells, i used heal, comet, lightning, hercules, protection, and pheonix.
Wait until you have a full force and full spells, then charge at the enemy. Stun the super goblin, use the pheonix, use hercules and protection. You should win no problem.
Destroying cop cars doesn't give you nearly enough of a bonus to make it worthwhile, since you can lose thousands by bumping into it enough times to destroy it. This game could use some work IMO.
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