MArcomage

This card is too strong, it creates a difference of 6 facilities (as crystal cavern) and it higly damages the opponent.
the most frustating games are games where your opponents keeps lowering your facilities and this card can kill 3 facilities in one strike. and it's also illusion.
I suggest to nerf it some way. maybe removing the facilities' gain or adding "can't lower an enemy facility under 2" or rise the cost.

I disagree. I think it's perfectly balanced for what it does.

And I think that this card is not so effective. It costs 45 gems - that's really expensive. And it's good only in resource stealing/destruction decks like Brigand/Destruction. Maybe it's also good in Charge or Nature decks - there's no way to spend gems when you play Charge, and Nature decks always have tons of gems and ways to reduce enemy stock.
Curse is a niche card, leave it as it is.

I condone, its cost is high enough to balance for the effect. There are other cards which lower your facilities for way lower cost and that have additional effects (i.e. the 3 destruction cards lowering each facility, cost about 12 gems each, total = 36 or Demolition Troops is another example). Plus, when you play Illusion, gems are vital. It's hard to hoard 45 gems without playing anything else

I think this card is nicely balanced. The cost per facility is less than the standard uncommon +1 facility cards, but more than Gateway. It doesn't get used very often (and even when people do take it, I don't often see it used very effectively), so that seems like an argument for it probably not being overpowered.

I think the odd thing about this card is that the AI seems to use it all the time. I haven't paid close attention to the deck(s) composition it's using, but it seems to be conserving gems rather easily. I'm guessing that people are noticing it more now since the AI is making better use of it than most players.

the AI builds up defences, raises cost and prefers playing common cards, thus accumulating stock to play high-costing high-damaging cards. It does use decks more effectively that way, but it rarely beats other people

Yes, it seems that AI has two signature cards - Curse and Damnation. I'm so proud of it ;-)