The 5th level spell Scrying allows you to attempt to magically spy on a creature. The caster doesn't even need to have met the creature to attempt this.
What happens when the target the caster has in mind could be multiple creatures?
As an example, a PC attempts to Scry a vigilante they have heard tales of. Unknown to them, this vigilante is actually 3 different people alternating shifts as the vigilante. Who does the spell end up targeting? Any of the people are a valid target for the spell, but which one attempts the saving throw to resist?