Ghasht, the Unsealer

Spellsurge —When you cast your second spell
each turn, exile the top card of your library. If
it's an instant or sorcery spell, you may cast that
card until end of turn.
You may pay X life instead of paying the
mana cost of spells exiled with Ghasht,
where X is that spell's converted mana cost.
"No cost too great."