I went with the assumption that the standard limitatons (attack action or targeted veil effect, failed attack or successful save against triggering effect negates, requires sneak attack conditions, 1 round duration), combined with the fact that the ability actually becomes available 3 levels after a sorcerer or wizard can start permanently blinding opponents, meant that adding a save to the ability would actually make it too cumbersome. Do let me know if that continues to feel too strong after you've logged some time on it though; I probably won't add a saving throw since I want to keep it as streamlined to use enigmas as possible, but if it starts presenting as a problem I can talk to Christen about the possibility of other limitations, like having it apply a penalty to the associated attack roll or saving throw.