[LDiCesare]

You can always get fire/death gems by using the so expensive acashic record. Better to target mountain regions which have either not been searched or have been but hold 0-1 or at most 2 sites.
Against Arco, you should beware in case the ai suddenly decides to send in elephants. My son experienced the fact that elephants tend to squish whatever front line you put between them and the archers, and it can be nasty if they reach the longbowmen.