If you would guess a card, instead just choose the outcome you want. At the beginning of each opponent's upkeep, look at the top card of their library. Tell them the name of that card. They tell you its mana cost, type line, power, and toughness. Then reveal that card. If they got anything wrong, draw a card.
Near Mint - $19.800
Lightly Played - $15.900
Moderately Played - $13.900
Heavily Played - $11.900
Damaged - $9.900
Near Mint Spanish - $19.800
Lightly Played Spanish - $15.900
Moderately Played Spanish - $13.900
Heavily Played Spanish - $11.900
Damaged Spanish - $9.900