Petrifying Gaze

If a target starts its turn within 30 feet of the creature and the two of them can see each other, the creature can force the target to make a Constitution saving throw (DC = 8 + proficiency bonus + Constitution modifier)if the creature isn't incapacitated. On a failed save, the target magically begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the target is petrified until freed by the greater restoration spell or other magic. A target that isn't surprised can avert its eyes to avoid the saving throw at the start of its turn. If it does so, it can't see the creature until the start of its next turn, when it can avert its eyes again. If it looks at the creature in the meantime, it must immediately make the save. If the creature sees its reflection within 30 feet of it in bright light, it mistakes itself for a rival and targets itself with its gaze. (Basilisk, pp. 24, MM)