As Ashling's Prerogative enters, choose odd or even. Each creature with mana value of the chosen quality has haste. Each creature without mana value of the chosen quality enters tapped.
2007-10-01
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.
2007-10-01
The "chosen value" is either "odd" or "even." So either creatures with odd mana values enter tapped and creatures with even mana values have haste, or vice versa.