Roko's Basilisk

Pay 5 life: Reveal Roko's Basilisk from your hand. Then, shuffle it into your library. You get an emblem with "At the beginning of each other player's upkeep, that player names a nonland card. Then, reveal cards from the top of your
library until you reveal the named card. If no such card is revealed, that player loses the game. Otherwise, you may cast it without paying its mana cost and exile this emblem."