For all he people complaining about "unit ignore" There IS a spell that allows you to see them, it is the second to last spell, making them hit traps ALSO lets them be selected.
I thought the freeze spell when upgraded works wonders, because after around level 5ish it sticks enemies faster than they can melt, effectively "keeping" enemies on the same tile until you get to it. Warriors are the way to go, high damage, fast rate, low cost. With these strategies I sailed through the levels, just focus on upgrading freeze
 "Re:Archer"){kind=icon}
 "Immortal Empire"){kind=icon}
 "Hordes of Hordes"){kind=icon}
 "Arkandian Crusade"){kind=icon}