FLIP: Send the top 5 cards of your opponent's Deck to the Graveyard.
Rulings
Individual Card FAQs
If there are fewer than 5 cards in your opponent's Deck when this card's Flip Effect is activated, all remaining cards in the Deck are placed in the Graveyard. The opponent does not lose immediately, but will lose if unable to draw a card when required (such as during their next Draw Phase).