White Sun's Nadir

( {p/u} can be paid with either {u} or {1} and 1 life.)
If {u}{r} was spent to cast this spell, draw 4 cards,
then discard 2 cards. If {b}{g} was spent to cast
this spell, return up to two target creature cards
from your graveyard to your hand. (Do both if {u}{b}{r}{g} was spent.) If at least four white mana
was spent to cast this spell, exile all creatures
instead.