Devouring Greed states:
As an additional cost to cast Devouring Greed, you may sacrifice any number of Spirits. Target player loses 2 life plus 2 life for each Spirit sacrificed this way. You gain that much life.
Does this only apply to cards that have a type/class of "Creature - Spirit" or does it include cards with a class of "Dragon Spirit" or "Demon Spirit"?
I have tried to research this but can't figure out the correct terms to search for.