Marnie is a double-edged sword. Though Marnie can quickly turn a good hand into a bad one for your opponent, it can do the same for you. When played, you draw 5 cards and your opponent draws 4. The rub is that you both have to put your previous hand at the bottom of the deck.
However, tricky or not, this is still a very playable card that will bring an element of surprise to many match-ups.