
When The Good Time Sleuth enters, exile the top card of your library and each nontoken creature you control in a face-down pile, shuffle that pile, then manifestmanifestLook at the top two cards of your library. Put one onto the battlefield face down as a 2/2 creature and the other into your graveyard. Turn it face up any time for its mana cost if it's a creature card. those cards. Then create a Blood tokenBlood tokenA Blood is an artifact token with ",
, Discard a card, Sacrifice this token: Draw a card." for each face-down creature you control. Those creature gain "Sacrifice a Blood: Turn this creature face up." Secretly choose one of them. As that creature is turned face up, reveal the choice and it becomes a 5/5 black Demon.
Hover an underlined rule to see what it means.
Read from the rules text. A card that enables a keyword makes or is the thing; a card that rewards it gets better when you have it. Two cards interact when one enables what the other rewards.