Muerte, Taker of Souls

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's colour.)
When Muerte, Taker of Souls enters the battlefield, destroy target creature an opponent controls if no {b} was spent to cast it.
{b}: Muerte gets +1/+1 until end of turn.
Living death.