Hello,
The Adventures expansion really had some interesting mechanics, many of which felt underused. Here are several ideas for cards that could fit right into the Adventures expansion (not really; as there are also some with Guilds mechanics). Without further adeu, here they are! They are ordered by price (and events are separated).
Coupon (Treasure, $2)
Exchange any number of +Buys for +1$ each.
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When you buy this card, you may overpay. If you do, gain an Action or Treasure
costing equal to the amount you have overpayed. Move your +Buy token to
its pile.
My goal was to create a $2 card that in itself benefits from many Buys, and that enables the +Buy token through overpaying. I like this version, though it might be OP when buys are plentifull.
Dwarves' Workshop (Action, $4)
Choose one: Move your -2$ token to an Action supply pile, or gain a card costing up to $4.
A workshop variant that makes good use of the -2$ token. May seem kinda OP, but it's also kinda slow at the same time.
Ecological Village (Action, $4)
+2 action, +1 card
When you gain this, you may move your trashing token to an Action Supply pile.
(when you buy a card from that pile, you may trash a card from your hand)
A village variant, and a more efficient version of Plan.
Robot (Action, $4)
Choose one: +1 action, +1$, +1 card or +1 buy. If this is the first time you played Robot this turn,
you may move your +action, +card, +buy or +$ token to its pile.
A card that moves teacher tokens to its own pile. It can become a strictly superior Grand Market, but it takes quite a few plays to get there. In that sense also a bit of a Traveller. I know a similar idea has also been brought in other threads, but I'd like to share it regardless.
Mystery Village (Action, $4)
+1 action
Play the card on the Mystery Village mat
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Setup: Put an action costing up to $3 that gives +1 action onto the
Mystery Village mat.
My favorite idea on the list, and probably better suited as a promo. It is a village that functions differently in each game, and can answer a lot of questions in the vein of "how would this card function if it was a village".
Housecleaner (Action, $5)
+1 card, +1 action
Draw cards untill you draw a Victory card costing up to $6. Move that card to the Tavern mat. Discard the rest.
This card enables Alt-VP strategies, as those VP cards won't be in your way now. The synergy with Disant Lands is intentional.
And now some events.
Money Pig (Event, $0)
When buying this event, you may overpay. +1 coin token per $ overpaid.
(Setup: Each player moves their +Buy token to the Silver pile at the start of the game)
This event is a perfect smoothener, but needs spare buys to work. The setup ensures that those are always there.
Reinforcements (Event, $5)
Gain an Action costing up to $4 that gives +1 action. Move your +Action token
to its pile.
A bit similar to Mystery Village, but more Adventures fitting. The idea is to get a cheaper version of Lost Arts that has far more limited targets, only allowing to make the Village of your choice.
Decorate (Event, $8)
Once per game: Gain a Duchy. Set aside a non-Victory Action card from the Supply costing up to $4.
Move your Duchy token to it (your Duchies gain the abilities and types of that card).
A Duchy version of Inheritance! Will probably play completely different. I decided to let it come with a Duchy, otherwise it is probably too inefficient.
And that's it! What do you think of these ideas? I may post some more in the future.