Rakdos Scherzo

Haste, Menace
Whenever Rakdos Scherzo attacks, exile the top card of each player’s library. Until end of turn, you may cast one of those cards, and you may spend mana as though it were mana of any color to cast it. Each opponent loses life equal to the exiled card’s mana value.

"A melody of madness, a dance of destruction—join in, or be torn apart by the tune."