Narvorth, the Misty Ruins

{t}: {c}{c}
When you cast a spell, you draw two cards.
{4},{t}: Exile an instant, sorcery, or enchantment and put two ruin counters on it. On your upkeep, remove a ruin counter. When there is no ruin counters, you may cast the spell without paying its mana cost. You may add one color of any mana for that spell's converted mana cost.