Darian, Molten Overlord

When Darian, Molten Overlord enters the battlefield, destroy any number of target creatures
with total power and toughness less than Darian, Molten Overlord's total power and toughness.
Whenever one or more creatures die, exile the top
card of your library, you lose life equal to its converted mana cost,
you may cast that card until the end of your next
turn.