[Finalgenesis]

I think rain of stone applies a 14 dam physical attack to the head (bladewind on every square, thus a magical projectile that can be parried)? Correct me if I'm wrong.

So a cheap 20 prot helmet should be pretty good insurance, a shield with good parry or air shield should be great too.

Usually I think you want to cast RoS (or multiples of) first turn to get in before or interrupt/kill battlefield wide protection/attack (WoTFate, gold/lead/fog warriors ...etc), assuming you are defending and going first (otherwise you are out of luck), just make sure your top unit ID caster (or at least before any RoS is cast) drop a fog or xxx warrior before you proceed to drop pebbles.