mtg theros commander decks guardians of the Abzan clan; Commander Series: List of Commander

Overall, the answer to "does the creature type matter?" is not especially

His "mandatory delve two" resource consumption makes him well balanced and interesting

The Twelfth Doctor was a teacher, and to demonstrate that, he works with the Demonstrate ability, letting you copy a spell you cast from anywhere except your hand

At the beginning of each end step, if a Creature card was put into your graveyard from anywhere this turn, create a 1/1 red Devil Creature token with When this Creature dies, it deals 1 damage to any target. This build mainly focuses on being a tribal like Devil and Demon deck

On top of that, Ancient Cellarspawn itself makes Demons, Horrors, and Nightmares cost one less