Dark Old Demon
Author, Sparda IS a Demon King. If not, then Dante shouldnt able to defeat Mundus in Mallet Island usind the Devil Sword Sparda that posses the power of sparda. And it should also be noted that Sparda survived the onslaught or hunting of the demons like demon lord, and demon kings like Samael for thousands of years despite all that, which means Sparda only sealed atleast half of his power in his sword, that was enough for Dante to defeat Mundus, and for Urizen the demon king to say that the devil sword spada has no longer a porpose/usefulness to him to empower him.