Card updates. I've done some more thinking and a little playtesting, and the following cards are updated:
Sect
Action - $1
+1 action
Trash a card from your hand
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When you buy this card, gain a curse, +1 card. Skip this turn’s cleanup phase. Take another turn after this one.
This is actually quite different in a few ways, and this probably makes it a tad weaker, but nicer rules wise. Firstly, treasures and actions in play won't actually do anything (they don't re-produce money). So don't play your treasures! Also duration cards activate, and you lose excess buys/coin/action etc.
Ceremony
Action - $3
Look at the top two cards of your deck. Reveal one and put them both into your hand.
If you revealed an:
Action card: +1 actions, discard a card.
Treasure card: +1 buy
Victory card: +1 cards. Put one cards from your hand on top of your deck.
Curse card: Trash a card from your hand.
Having thought about rinkwork's advice, this is a very similar idea but a lot more interesting. Now it's benefits can depend on what you draw: It could be a cantrip sifter, draw+buy, or Courtyard, or if you get multi-type cards, some combination. This might even be too weak now, but at least you get some control over the benefit.
Community
Action - $3
+2 Actions
+1 coin for every two actions in play, including this.
Not a change, but it got a name. I'm happy with how this played. We ended up building a deck that used these to give like +$6 coin, but it took far too long. And if you use it early for just +2 actions, you aren't getting as much money as you could. It needs some proper playtesting (as in, where we don't go for near identical decks) but I'm pretty sure it's at exactly the right power level.
Wedding
Action - $4
Trash two cards. If you do, choose one: gain a Duchy, putting it on your deck OR gain a silver.
This card has had a strange development. It started as something like (shortened version) 'reveal 5 cards from your deck and any victory cards in hand. Trash any number of victory cards, gain a victory card giving [restriction on types that basically meant trash 3 estates, gain a Duchy]'. Then it changed to something very similar to the version I posted (I think it allowed the Gold to be top-decked and the Duchy wasn't, which was massively overpowered in many cases). Now it's this. I think this should work better.
Dowry
Action - $6
+2 Cards
+$2
Just a price increase. A sort of middle ground between rinkwork's thoughts and my own, it could still be adjusted later.
And new cards!
Mercenary
Action - Attack $5
+$1
Each other player reveals the top card of their deck. If it is an action or treasure card costing $3 or more, they trash that card and may gain a card costing at most $1 less than it. If they do not trash the revealed card, they discard it or put it back, your choice.
Each other player discards down to 4 cards in hand and gains a copper.
The attack version of JoaT. It has a weak saboteur or spy effect, followed by a weak discard, followed by a weak junking. Together it makes a card that's not quite as dominant as JoaT but seemed pretty decent in general. It seemed to be about the right level of power.
Mysterious Gift
Treasure - $0
$1
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When this card is trashed or revealed, reveal you hand and discard all the revealed treasure cards.
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When you buy this card, +$3 and buy an action card.
I love my strange card costs, right? Actually, I was thinking of making Sect cost $2*, costing one less during your buy phase (but not less than 0). But I digress. It's a copper with a penalty. What an amazing idea. But of course it has a powerful benefit as well, letting you grab expensive actions when you otherwise couldn't afford them. Opening Cartographer/Mysterious Gift/Mercenary sure was fun, though. This card is probably at it's strongest in big turn engines, or heavy action engines, as the potential discard effect will hopefully cause little damage, and grabbing power actions early is a big plus. Turn 1 Forge anyone?