So I was thinking both of an Attack-Reserve card as well as a Reserve "Moat" kind of card, and I realized it would be neat to have an Attack that put other players' cards on their Tavern mat. This is also flavorful - a Sheriff puts opponents' cards in "jail", and sets your own cards free. It couldn't hit Victory cards, because that would be too automatic, or other Reserve cards, because that's actually helpful for them. Sure, it'll hit Coppers, but that's also decreasing their spending for that turn, like Cutpurse.
As for the "Moat" part, a Reserve "Moat" would have to be an Attack itself, so there's something it can be called to do.
Sheriff
- Action-Attack-Reserve
+
You may discard a non-Reserve card from your Tavern mat. Each other player with at least 5 cards in hand puts a non-Reserve Action or Treasure card from their hand on their Tavern mat (or reveals a hand with no such cards). Put this on your Tavern mat.
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When another player plays an Attack, you may call this, to ignore its effects.Actually, I'm realizing this shouldn't have a Moat part or a Reserve bit. It should just be:
Sheriff - Action-Attack
+
You may discard a non-Reserve card from your Tavern mat. Each other player with at least 5 cards in hand puts a non-Reserve Action or Treasure card from their hand on their Tavern mat (or reveals a hand with no such cards).