[Micah]

Don't forget that since clams are items they can be yanked out of the castle in question and redistributed before any assassination attempts occur, even if you were able to kill a patrolling army deep in enemy territory. So now we're talking about a large force and/or several SC's teleporting/Astral travelling into a province (since you can bet that it'll be patrolled by stuff that'll kill a single SC off easily) and then spamming remote attack spells at every location that's likely to have a lab and a couple of commanders in it.

Oh, just remembered, all those domes prevent travel spells, don't they? Well, now we're talking about teleporting in next to the target province and then attacking it the next turn after showing the defender the composition and capabilities of your army from taking out the PD. Maybe you could put scouts there and then outfit your SCs with stealthed-in items for surprise. Good luck with that.

There is no effective counter to clams. Guarding 5-10 forgers from Corruption horrors to get them into play isn't that hard, and once the clams are made they're nigh-impossible to get rid of short of the complete destruction of the owning nation. They don't show up in the income graph, and they're maintenance-free. Leaving them in the game is going to be akin to making them like recruiting troops. There might be some other stuff you can do with your gold besides buying troops, but you kind of have to do it to some degree.

Flames from the sky has about a 5% chance of getting through a quadruple-domed province, and costs 35 gems per cast, so that's about 20 castings, on average, or 700 fire gems. It will hit half of the units, and kill most of them if they're in the realm of 10 HP, so that means your attacker has to expect that there are about 1500 gems' worth of clams in a province to make it cost-effective to spam Flames, which works out to about 1 castle/quadruple dome/patrolling army per 50 clams to be on the safe side of the cost-effectiveness curve. Even with some liches crawling around to spam Drain Life on any teleporting SC that might come calling that's not a particularly heavy infrastructure investment to keep your clams safe. Add in the obvious problem of actually figuring out where the clams ARE and the advantage for the defender in this situation is pretty insurmountable.