[Boron]

The lvl 9 spell iirc flames from the sky is very good . It wipes out scouts very well and that is the most imortant thing . This balances Clamhoarding because if you have more then 30 clamhoarding scouts in a province they are a nice target for flames from the sky .
If you have e.g. 50 Provinces and 1000 clamhoarders if you divide them equally to the 50 Provinces you still have 20 Scouts per Province = excellent Flames from Sky / Afar Targets . If your enemy conquers some of them you have to concentrate your scouts even more and they get even more vulnerable towards flames .

Thus those 2 Spells Balance Clamhoarding very well . You rarely can have more then 1000 Clams without risking to lose them easily .
1000 Clams = FotA 20 turns up , with some Nations like a lucky Mictlan this is quite possible .