[Tuidjy]

K, I have to disagree about water magic. It is useful for both summoning
(the shark line of spells), army support (friendly currents) and SCs (quicken
self, water shield, breath of winter) Niefel Jarls, for example, are beasts
underwater. Or anywhere, for that matter, except for hot provinces.

Against the AI, I suggest SCs. If you control the landmass, and have an
abundance of gems, Wraith Lords with firebrand, charcoal shield, spirit helmet,
chainmail of displacement, coots of quickness, ring of regeneration, and amulet
of luck are able to take on any amount of troops.