Jan 25, 2016
In the instance of Edgewalker, there is a specific type of mana included in the cost reduction. Since the previous version of printing {C} on cards that produce colorless was just 1, could it be interpreted that errata on Herald of Kozilek is “Colorless spells you cast cost {C} less to cast”?
No, it couldn’t. There are no cards that reduce a spell’s cost by C. No cards are being changed to reduce costs by C.
Herald of Kozilek, Animar, Mizzix and other cost reduction effects still reduce costs only by generic mana.