Blinding Flash

Using an action you may cast a flash of blinding white radiance from yourself. Any creatures within sight of you must make a Constitution saving throw. On a failed throw that creature is considered to have the blinded condition for 2  rounds of combat and half as many on a successful throw.

The radiance is instantly cast and fades immediately after, thus a creature, if warned, may take a bonus action to cover their eyes prior to spell being cast to prevent the effects of the spell.