I really like the idea of a Duration that stays in play until your opponent does something. I'm a little concerned about the politics of a multiplayer game.
And +2 cards, +1 buy feels like a strange effect for a card that in theory you might only play once ever. I dunno if that's actually based on anything; just a feeling I get. Maybe because I'm comparing it to Reserve cards, which are all either +1 action, cantrip, or nothing on play.