[Juzza]

You know what'd be a cool? a spell called "Boil The Oceans" though you'd have to incorporate a 'water level percentage' This would determine weather the water is Sea or Deep sea. Now as for the spell! Fire spell, level 9, in a fitting school of magic anyway, it slowly, boils the oceans away leaving wastelands in it's wake. All aquatic creatures die, and armies from the lands can walk in the now empty seas. The oceans would remain dry until the spell is dispelled or the caster dies. However, not all underwater nations has astral magic and the most vulnerable nation, to this spell would be early age Oceania which has nearly all aquatic unit, I'd suggest a water spell that envelopes one province totally in water, the spell would only be able to be cast while there there is a water percentage left in the province.

Oh, and sry it's a lill' off topic, but it would make it easy to take out sea nations eh?

Except if they dispel it, then wooosh!