you can beat cave 5 by having units goblins,centaurs,dwarf engineers,witches,black knights and mermaids spells comet,heal,hercules strength,lightning,freeze all upgraded to level 5.
at first, have your hero close to the bombs but so that they can't see you and when your hero marches,tell him to go back to the old place so that he doesn't hit the bombs and heal him when he's at low health and make sure the other units are idle and when there are many bombs blast them with comets and when all of the units have spawned to the battlefield click march.
when the units reach the castle, use hercules strength and when the invincible goblin tries to hit you,use freeze and when there isn't any freeze left, use lightning.+ so people can know and also you get a berzerk spell from this fight and berzerk+hercules strength+phoenix= 17k damage.
Tips:
-For the one complain about revenge waves, and complain that its unfair, let me tell you that you have skill cards and you can regen your unit which enemy couldnt do that.
how is this a tip?
Comment this up so people don't get stuck on beating the final level: Get the fastest troops, cassandra, popo and kara as heroes, and get the celest angel and sky dragon - make your heroes and everything else attack as SOON AS THEY ARE LOADED, because when the yeti comes they'll die. Use the shield whenever it runs out, after there's 2 seconds left. Only after the giant yeti comes out, though.