General impossible difficulty (no loss)

[Zechnophobe]

Level 5's are perfectly viable, due to Turn back Time spell. Since you can resurrect an infinite number of level 5's, so long as they all die in the appropriate turn order, it makes them very efficient tanks, especially fast moving ones like red dragons or Ogres. Frankly I spent the majority of my impossible, no kite paladin game using 3 or 4 (occasionally 5!) stacks of level 5 units. They just don't DIE very often, and target on the first turn can often make for an effective TBT on the second turn.