The Joker, Jester of Genocide

When The Joker enters the battlefield, you may sacrifice a permanent to cast a creature card from
your hand without paying its mana cost. If a spell
is cast this way, you lose life equal to its mana
cost.
"But here's the cold, hard truth, Bats. I don't hate
you 'cause I'm crazy. I'm crazy 'cause I hate you."
- The Joker