Molten-Tail Masticore [Scars of Mirrodin]

At the beginning of your upkeep, sacrifice Molten-Tail Masticore unless you discard a card.
{4}, Exile a creature card from your graveyard: Molten-Tail Masticore deals 4 damage to any target.
{2}: Regenerate Molten-Tail Masticore.