不能，只能是0。如下所示：
If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost. (2018-07-13)
If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost. (2018-07-13)
