Sure, I'm doing some testing
Unit Order
Sorcerer N2D1F1 - Swarm of Spiders - 1 gem in inventory (
Spell cost: 1) - 0Gems used = Didn't cast.
Sorcerer N3D1F1 - Swarm of Spiders - 2 gems in inventory (
Spell cost: 1) - 2 Gems used =
Fatigue 35Sorcerer N2D1F1E1 Swarm of Spiders - 2 gems in inventory (
Spell cost: 1) - 2 Gems used =
Fatigue 52Sorcerer N1D1F1 Swarm of Spiders - 10 gems in inventory (
Spell cost: 1) - 1 Gem used =
Fatigue 102 - didn't cast Swarm of Spiders (which needs N2D1 - instead used "Swarm" which is N1 and costs 100 fatigue) - casts it again when under 100 fati.
Black Soc F2 E3 D1 N1 - Curse of Stones -5 gems in inv (
Spell cost: 3) - 3 gems used ?
Fatigue 200 - Curse of Stones has a fatigue cost of 300- the Caster only had 200 after using the normal cost of gems (3) - max limit of 200 fatigue on one cast?
Pretender N4D4 - Swarm of Spiders - 30 gems in inv - (
)- 2 Gem used = Fatigue
cost/cast 23 [107 Fatigue after 5 casts] - continued to cast at 23 cost whenever he could. - ended the fight with 9 gems total left, so 21 used. Maybe he changes casting to use more gems/cost less over 50 fatigue?
I can at least somewhat get them to do what I want, but after the first cast, all bets are off.
Edit: Mage F4 - Will 'o'wisp (costs 1, fatigue 100-) - he used 3 out of 10 gems and suffered 24 fatigue damage - if they can waste gems, they will...
Mage F4 - Summon Fire Elemental - cost 1 - Fatigue 100 3 gems used and 34 fatigue damage
Mage F4 - Summon Fire Elemental - cost 1 - Fatigue 100 4 gems used and 28 fatigue damage
So with this I can confirm - he will pay more gems if above 50 fatigue or so and try his best to stay under 100. - AI choose to pay 3 gems (instead of possible 4) while under 50 fatigue, but then used 4 while above it, for the same spell.
Various other notes:
The Spiders from Summon-Swarm are pretty worthless against normal chaff - there poison does no real damage(5-10 points of fatigue dmg), there bite is 1 dmg. You get 70, but 70 only manged to kill 2 basic barbarian soldiers - seeing how you need to nearly always use 2 gems to get them cast'd
Master of the Games is a beast in any kind of fair combat - except vs fire elementals which ruin his day
125 is the max defence value you can buy
Units set to patrol will defend the province attacked and NOT hide in the castle.
Argartha is really hard to fight, when it gets enouch resources to get a army up