Rhea, Mother of Gods

Rhea costs X less to cast, where X is the number
of Titan creatures you control.
Whenever you cast a spell, exile cards from the
top of your library until you exile a nonland card
that costs less. You may cast it without paying its
mana cost. Put the exiled cards on the bottom of
your library in a random order.
Rebirth - {w}{u}{b}{r}{g}, 5