火の玉
ソーサリー
望む数のクリーチャーかプレイヤー（またはその組み合わせ）を対象とする。火の玉はそれらに、Ｘ点を均等に割った点数のダメージを与える（端数切捨て）。
火の玉を唱えるためのコストは、２つ目以降の対象１つにつき
多くなる。
Illustrated by
Magic 2011#138UncommonJapaneseLegality
Rulings
For example, if X is 5 and you choose three target creatures, Fireball has a total cost of 
(even though its mana cost is just 
and its converted mana cost is 6). If those creatures are all still legal targets as Fireball resolves, it deals 1 damage to each of them.
You may cast Fireball with zero targets, regardless of the value chosen for X. If you do so, it will not be a targeted spell, and no damage will actually be dealt when it resolves.
Fireball’s damage is divided as Fireball resolves, not as it’s cast, because there are no choices involved. The division involves only targets that are still legal as Fireball resolves.
You can target more than X creatures. However, if the number of legal targets at the time Fireball resolves is greater than X, none of them will be dealt any damage.