Devoid (This card has no color.)
{3}{C}, Exile a creature card from your graveyard: Target opponent loses life equal to the exiled card's power. ({C} represents colorless mana.)
A creature token is not a creature card. Although a token does go to the graveyard briefly if it dies, it ceases to exist before you have the opportunity to do anything.
Use the card’s power as it last existed in your graveyard to determine how much life is lost.