Q: When a card refers to an effect that occurs when a spell is cast, can this spell be the summoning of a creature? For example, "Throne of Bone" allows a player to tap one land and gain one life and says "Use this ability only when a black SPELL is successfully cast and only once for each such spell."

A: A spell is any card other than a land. For example, the Black card "Feral Shadow" is technically just a spell that summons the Feral Shadow until it comes into play, at which point the card becomes the creature.