Ashling's Prerogative | Magic: The Gathering
Formats Ashling's Prerogative is Legal in
Official Oracle Text for Ashling's Prerogative
Each creature with converted mana cost of the chosen value has haste.
Each creature without converted mana cost of the chosen value enters the battlefield tapped.
Official Rulings for Ashling's Prerogative
10/1/2007 : If a creature has X in its mana cost, that X is treated as 0 for the purposes of these effects. It doesn't matter what the value of X was while the creature was on the stack.