Horrific Appearance

Any humanoid that starts its turn within 30 feet of the creature and can see the creature's true form must make a Wisdom saving throw (DC = 8 + proficiency bonus + Charisma modifier). On a failed save, the humanoid is frightened for 1 minute. A humanoid can repeat the saving throw at the end of each of its turns, with disadvantage if the creature is within line of sight, ending the effect on itself on a success. If a humanoid’s saving throw is successful or the effect ends for it, the humanoid is immune to the creature's Horrific Appearance for the next 24 hours. Unless the humanoid is surprised or the revelation of the creature’s true form is sudden, the humanoid can avert its eyes and avoid making the initial saving throw. Until the start of its next turn, a humanoid that averts its eyes has disadvantage on attack rolls against the creature. (Sea Hag, pp. 179, MM)