Fireball
Sorcery
The spell fell upon the crowd like a dragon, ancient and full of death.
Rulings (4)
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.
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.
For example, if X is 5 and you choose three target creatures, Fireball has a total cost of 7 generic mana red mana (even though its mana cost is just 5 generic mana red mana and its mana value is 6). If those creatures are all still legal targets as Fireball resolves, it deals 1 damage to each of them.
Legality
Formats by platform