Norath, The Harvested

Whenever you gain life you may pay 2 life,
if you do untap Norath, The Harvested.
{t}, Pay 2 life: Exile target card from a graveyard.
{t}, Pay 4 life: Add {w}, {b}, or {g}.
{t}, Pay 6 life: Destroy target nonland permanent with mana value 4 or less.