Merge the343danny's idea and xienwolf's idea from two posts up and it'd be perfect.
Temples of the White Hand act as seeds. Ice spreads across Illian lands, similiar to how hell spreads. It stops at Illian borders....
until...
AA is in the game, now it just spreads everywhere until he is dead. Then either it "melts" in non-illian lands or simply ceases to spread and non-illians can terraform it as they see fit.
Of course, in order for this to work right Illian-Snow/Ice tiles would need to be always on par with the regular quality tiles. There are a few instances where the Illians lose resources for ice/snowing tiles. The spread of ice/snow would have to be universally a good thing for Illians prior to the above ideas...
Temples of the White Hand act as seeds. Ice spreads across Illian lands, similiar to how hell spreads. It stops at Illian borders....
until...
AA is in the game, now it just spreads everywhere until he is dead. Then either it "melts" in non-illian lands or simply ceases to spread and non-illians can terraform it as they see fit.
Of course, in order for this to work right Illian-Snow/Ice tiles would need to be always on par with the regular quality tiles. There are a few instances where the Illians lose resources for ice/snowing tiles. The spread of ice/snow would have to be universally a good thing for Illians prior to the above ideas...