Marcos, Father of Chaos

When Marcos Father of Chaos enters the battlefield or at the beginning of your upkeep, create a 1/1 black shadow creature token with fly
and "When this creature dies, it exiles the top card from each player's library, you can play the cards while in exile, and you can spend mana as if it were mana of any kind to cast that spell"
Sacrifice a creature: Scry 1, then draw a card