Spell Incarnate

Whenever an instant or sorcery is played, exile Spell Incarnate. When that spell resolves, it becomes a X/X elemental creature instead of going to the graveyard, where X is the spell's converted mana cost.
If that creature would leave the battlefield, exile it and return Spell Incarnate to the battlefield under your control.
I-N-C-A-R-N-A-T-E