Cone of Flame
Sorcery
Cone of Flame deals 1 damage to any target, 2 damage to another target, and 3 damage to a third target.
Chippy
Rulings
If one or two of Cone of Flame’s targets are illegal when it resolves, you can’t change how much damage will be dealt to the remaining legal targets.
(wotc • 2014-07-18)
Each of the three targets must be different. If there aren’t three different legal targets available, you can’t cast the spell.
(wotc • 2014-07-18)
Rulings
If one or two of Cone of Flame’s targets are illegal when it resolves, you can’t change how much damage will be dealt to the remaining legal targets.
(wotc • 2014-07-18)
Each of the three targets must be different. If there aren’t three different legal targets available, you can’t cast the spell.
(wotc • 2014-07-18)