I was thinking about tunnel, and also how annoying it can be to discard your only platinum to an opponent's Tribute or have your Sea Hag get Sea Hagged, and I wondered if a reaction could be made to turn that kind of deck cycling into a benefit. This is far to weak for a pure reaction, so it would need some kind of action component as well, but I thought it would be a cool idea.
Reaction:
If a card is discarded from your deck, you may reveal and discard this card. Place the discarded card into your hand.
I was also considering a secondary benefit, i.e. Place the discarded card in your hand and draw a card or something.
For the action component, I think something thematically related could be a card that retrieves something from your discard pile, ala Counting House, but for something other than coppers. But that has the potential for some extremely broken combos.
I know the usual M.O. on this board is design first and ask questions later, but I wanted to throw open the gates on this one. What do you guys think of this idea? Too situational?