skigglez Keeper added the retaliation thing and I haven't looked at the code for it, but I don't believe offensive spells break protection - someone can correct me if I'm wrong on that.
Theres no KS limit perse (fireball does have a limit, but it's pretty high % of pop that can die limit), but it is much more difficult to hit-up with a than down - as the defenders land and KS are figured into the difficulty, and the difficulty level also effects the potency. A caster doing a fireball on someone same size or smaller can kill more pez per wiz than if they fireball someone that's bigger than them.
The potency is a really interesting formula, since it takes so many things into consideration - including the defenders size, their schools, their wizards, their rested vs unrested wizards. The formula that figures out success is also used in the potency, so if you do have schools and wizards then you can reduce the potency of a offensive spell cast on you.
Rested wiz count for double what a resting wiz counts for.
Then on top of all that, there's the 300 sided dice that also plays a part. If a caster rolls a 300 crit, then even a reasonable defence of schools/wiz won't feel like it dampened the effects much. While a really low roll might make the caster feel a bit cheated.
Overall I think the magic system is pretty well balanced, with a bit of chance thrown in for fun. Definitely makes people think twice about running no magic defense now that the elves are turning into glass cannons.
In that respect, maybe giving offensive spells a retal wasn't such a bad idea after all 😵💫