I don't like Spymasters as it has already been considered by DXV (Secret History of Empires: "I tried a giant Pawn briefly.").
It would probably be OK at 6 too (mostly used as Lab) and I don't think that some hyperflexible card leads to interesting play.
Demagogue should feature a non-Demagogue clause (to prevent infinite loops) is cool and is probably OK at 4 due to the strong alternative option.
I have no idea how to play well with the DarkAge-y Kurgan but I like it.
Commission is a Treasure version of a something a bit weaker than Caravan Guard aka delayed Peddler (as the card and not the coin is delaed). Nothing fancy but balanced.
Foothills isn't bad but boring: it rewards what you want to do anyway.
Ancient City on the other hand creates a nice incentive to not go for mono-card strategies and, come on, who doesn't like Cornucopia-esque variety-rewarding cards.
My thought with Spymasters being 7 was not "having one copy of this card is so good it ought to cost 7"; it was more "this card is so good in lots of multiples that I want to make it hard to obtain several". I agree it's not the most interesting of ideas, but it's still fun to think about, and it's nice because it would basically never be dead.
Good catch on Demagogue. I'd like to actually play with this card to see how strong it is, but I agree that 4 isn't unreasonable.
I think the play with the Kurgan landmark would be interesting, because obviously you can get lots of points from keeping a Copper, but so can your opponent, so in that regard it's a lot like Fountain. I think the interesting bit would be where you want to trash actions that you have a copy of, or not play self-trashing actions. The Victory card would reward trashing single copies of actions you have, at least if you win the Kurgan split; I think it works better as a Landmark because it doesn't suffer the problem with victory cards based on the trash where whoever loses the split has no incentive to make their copies better, since they're based on a common resource, and basically no way to make them worse.
Here's another card, which I admit that I came up with entirely for the gimmick of having a card with five types, but which I think is actually a decent card.
Roving Bandits - $5 Action-Attack-Looter-Reaction-Duration
Now and at the start of your next turn, each other player gains a Ruins, and if they don't, discards a card and draws up to 4 cards in hand.
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When another player gains a Gold, you may trash this from your hand, to instead gain that Gold.