Whizbang Dustyboots
Gnometown Hero
How does it work when the wizard can't see everyone who might be affected, like when they're firing a spell into the fog or a dark cave? As written, the wizard doesn't need to see who the targets are to be able to narrow who's affected by a modified spell.It is more like, the Wizard is firing a gun. The target is, by definition, the "foe". The others who Wizard is trying not to shoot are "allies".
It depends 100% on the Wizard
It has nothing to do with intentions of the targets.
Indeed, an "ally" might be plotting to harm the Wizard. But if the Wizard is uninteresting in shooting this "ally", it remains an "ally" sotospeak.
WotC needs to add a sentence or two to clarify this aspect of the ability.