What u have to do is modify the attack types and armor. For example if knights have Large Armor, u can modify it so it takes extra dmg from magic atk. To do so, Go under the Advanced Tab, i dont remember which but click either Game Constants or Game Inferface. At the top of one of them should give u a table of Attack types which u can modify according to percentage. Magic atk by defult alrdy does extra dmg to what the type of armor knights have.
TheMoneyLover, you missed the problem. there are TWO types of magic, so that takes up TWO attack types. which may or may not be a good thing. you could set up a trigger where if a spell is cast, condition that the unit targeted by spell is a knight, deal a certain amount of damage.
i confused you? YES somebody other than me got utterly confused by something not-so-utterly confusing! if you set it up the way TheMoneyLover is telling you two, it would take two types of attacks. ie, take normal damage from spells EXCEPT for lightning. from lightning they take extra. actually, that would take as many attack types as you have spell elements, attack types of which there may not be enough of. about the trigger, use the same stuff but the action would be deal <damage> to target of spell.
well of course it is. set up the actual spells to do the damage that you take if you're resistant to the spell type. set up triggers that deal the extra damage to units that aren't, and even more extra damage to units that are weak to it.