Here is my submission (there are 20 in the pile)
I know Donald X. has said that Rats is his favorite card (that was said some time ago, I don't know if it still is). It's one of my favorite as well. There's something so great about the finesse that's required to play a card like that. On the one hand you want to play a bunch of them and gain a bunch them to tfb, on the other hand, you can't let rats overrun your deck. With that in mind, I've always wanted to make a card that fits in that idea. Here is what I came up with. It's a self gaining lab, but you have to be careful about playing too many of them or you'll destroy the rest of your turn (make sure to keep the riot under control).
1) Just to preempt any discussion about price, keep in mind that when it comes to self gainers, a higher cost actually makes the card a more worthwhile buy (would you buy rats if it cost $2?). You only buy it once, but you'll can tfb it multiple times.
2) The bottom part applies to all cards that you play (actions, treasures, night), but only when you play them (so calling a reserve would work).
I have to ask the community for advice on 2 things:
1) The copper clause has a bit of history. First there was no clause. But then I felt it would too punishing to play your first riot and the barrier would be too great since you often play a couple of coppers each turn in the early game. So then I specifically excluded copper. But then I realized you could buy one copper (to have 8 ) and a riot and just play a bunch of riots and play 8 coppers and get a province. So then I made it that copper costs 3 more if you have a riot in play, but realized it could be abused with tfb like farmland or remodel. So finally this is what I have.
I'm wondering if anyone has a better way to word it (especially if you could combine both parts under the line).
2) I was debating adding a little bonus for trashing this (like rats). I was thinking maybe +1 action or you may trash a card. Do you guys think it's good as is, or should I add a bonus (and which one)
Thanks
Update: Fixed Copper issue below line