Those of you that played in the prerelease might very well know what a formidable card Warden of Evos Isle can be; an aggressively costed evasive beater that makes your other flying creatures even cheaper! The important thing about Warden is it only checks whether or not the creature spell has flying when you cast the spell; it doesn’t matter if your creature would or could have flying once it hits the board, it has to have “Flying” printed on the card itself. Are you casting Clone, with the intent to copy Warden? It’ll cost you 3U, not 2U. Are you casting a Sliver creature while you control Galerider Sliver? The cost of this sliver spell won’t be lowered, as the Sliver won’t gain flying until it enters the battlefield. It doesn’t matter how many dozens of times over the creature WOULD have flying on board; unless it’s got wings from the get-go, Warden won’t give you a discount.