Cleric of Joy

Madness {2}: (if you discard this card, discard it
into exile. Then, you may cast it for its madness
cost or put it into your graveyard.)
When Cleric of Joy enters the battlefield, add {c}{r}{g}.
Whenever another creature enters the battlefield
under your control, exile the top card of your
library. Until end of turn, you may play that
card.