Simple deck that will beat all 18 levels easily: I call it Kamikaze Deck!
All you need is:
All of your Peasants (or other cheap summons) + keep the Universal Effect card "Parting Gift" in play the whole game. (use 2 or 3 in your deck in case the opponent cancels it) With this effect in play, each peasant the enemy kills does 1 damage to the enemy portal. Just spam peasants and voila! Easy win.
Round out the rest of your deck with nothing but resource cards.
Keep this bumped!