They're like throne rooms, but for Hinterlands cards : throne areas. And, not to make them dead cards in game without "on-gain" cards, I put some self-synergizing effect
-Throne area (A)-
Action, $6
Choose an action card from your hand. Gain it twice.
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When you gain this, gain a card costing less than this.
-Throne area (B)-
Action, reaction $6
Choose an action card from your hand. Gain it twice.
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When you gain a card, you may discard this from your hand. If you do, gain a Gold.
And then, a really bad "really bad card ideas" idea...
-Contraband (LG)-
Treasure, $5
Worth $2, +1 buy.
When you play this, take a Treasure card from your hand, face down (or reveal a hand without Treasures). The player to your left either call "pass", or "check $X" with $X equal or larger than $2. Either case, reveal the card you have taken.
-If your opponent called "pass", +$1 and play it as usual. Otherwise, count $Y, the amount of $s that card generated.
-If $Y is between $2 and $X (included), discard that card and he gains $Y during his next turn
-Otherwise ($Y = $0, $1, or $Y>$X), +$X and play that card.
If you don't have the reference, LG in the card name stands for Liar Game, an excellent manga that you Dominion players should read.
Edit : added a +$3 so people don't always want to call "pass". Plus it becomes closer to a well-known official card...
Edit : changed a bit the things, so people won't always call "check $2" (before it was Worth $0 by default and worth $3 if he called "pass"