Warlock with Beshadowed Blast can blind targets if target fails to make a DC check against 10 + Spell level (4) + Caster level
Beshadowed Blast indicates:
This eldritch essence invocation allows you to change your eldritch blast into a beshadowed blast. Any living creature struck by a beshadowed blast must succeed on a Fortitude save or be blinded for 1 round.
And blinded creatures are:
The character cannot see. He takes a –2 penalty to Armor Class, loses his Dexterity bonus to AC (if any), moves at half speed, and takes a –4 penalty on Search checks and on most Strength- and Dexterity-based skill checks. All checks and activities that rely on vision (such as reading and Spot checks) automatically fail. All opponents are considered to have total concealment (50% miss chance) to the blinded character. Characters who remain blinded for a long time grow accustomed to these drawbacks and can overcome some of them.
What sort of creatures does not need to make this save since they can’t be blinded?