Enchant nonland permanent At the beginning of the upkeep of enchanted permanent's controller, that player sacrifices it unless they pay {X}, where X is its mana value.
2012-10-01
If the permanent has {X} in its mana cost, X is 0.
2012-10-01
The mana value of a creature token is 0, unless that token is a copy of another creature, in which case it copies that creature's mana cost.