Ambushing Behlam
Behlam Dorian had night blindness from when he was a kid.
Usually, impairments like these would get cured when mortals became rankers. But Behlam experienced mana circuit anomalies when he was breaking into the Meta rank. This forced him to live with the handicap he was born with even when he had entered the Awakened rank.
Behlam felt his night vision improving when he broke into the Awakened rank. But it was a far cry from the normal vision he would have when there was enough light. All he could see at this point was a blur.
For obvious reasons, Behlam kept this secret closely guarded. He didn't tell anyone in the guild about it. But a perceptive person like Ariadne had guessed his condition after seeing him operate in a previous job before the cultist hideout mission.
She saw that Behlam would depend on his mana sense more when it was nighttime. It allowed him to function as a normal ranker even though he could see almost nothing with his eyes.