I had a card that did it with your own deck. It sounds so innocent, but I seem to remember it being easy to basically have a deck that essentially hid away it's victory cards. But I can't remember for the life of me how that went, or why it happened.
Edit: Oh and you need to shuffle, or the time you lose from ordering discards will be insane. And you don't want it to be a cantrip, because playing multiple per turn will be unpleasant but I suspect sometimes optimal.