Possession Alternative $6P
Action-Duration
At the start of your next turn, +1 Buy.
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While you have a Possession Alternative in play:
When another player gains a non-victory card, you may gain a copy of it.
When another player ends their buy phase, they reveal their hand. Take a coin token per Treasure they revealed and remaining unspent coin.
So Possession has many problems:
1. It is unfun (to watch people use your deck, especially multiple times)
2. It can be swingy
3. Can be political in multiplayer
3. Too many wonky rules interactions, especially in newer sets
Thinking about these problems, I tried to make a card similar to Possession without having the above problems. What Possession does is to take an extra turn out of your opponent's deck. Following that, I tried to simulate that by giving you what you could've gotten out of your opponent's turn.
So I ended up with gaining a copy of whatever your opponent gained. To make the game not a complete deadlock, I disallowed gaining victory cards, as well as wording the bottom part to make it unstackable. To disallow opponents from evading it completely, I added the bottom clause to discourage such behaviour.
I needed it to do something on the next turn to make the card work (like with Swamp Hag, Haunted Woods, Enchantress), so I decided to give +1 buy to go with the extra coins amassed.
This scales in multiplayer, but I think it's better to affect all opponents equally to make it less political.
I haven't tested this and I believe there are ways to improve this, please give suggestions if you have any.