Familiar vs. Spy
Am I alone in thinking that this is the biggest imbalance between the Kingdoms and Empires?
The summon familiar spell gets you a weak little demon-looking-thing that does triple damage on counter-attacks.
The summon spy spell gets you a weak little demon-looking-thing that can cast a spell to damage every enemy on the screen for 10 points.
That 10-points-to-all ability is so powerful, especially at early levels, but it's useful all throughout the game. The Kingdom's familiar really needs to be buffed to match it.