Petrifying Gaze. If a creature starts its turn within 30 feet of the basilisk and the two of them can see each other, the basilisk can force the creature to make a DC 14 Constitution saving throw if the basilisk isn't incapacitated. If the target fails the saving throw by 5 or more, it is instantly turned to stone and petrified. Otherwise, on a failed save, the creature 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 creature is petrified until freed by the greater restoration spell or other magic.

A creature 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 basilisk until the start of its next turn, when it can avert its eyes again.

If it looks at the basilisk in the meantime, it must immediately make the save.

Scent Tracker. When a basilisk damages a creature with its bite, it can sniff the creature’s blood as a bonus action. Until the creature’s wounds are fully closed, the basilisk has advantage on perception checks using smell to detect the creature. If it uses this feature again, it forgets any previously learned scent.

Squeeze. The basilisk can fit through any path large enough for a small creature.

Bite. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 17 (4d6 + 3) piercing damage plus 14 (4d6) poison damage. The piercing damage from this attack deals full damage to petrified creatures. It the target takes any poison damage from this, it must succeed on a DC 14 Constitution saving throw or be poisoned for one minute. It can repeat the saving throw at the end of each of its turns, ending the poison on a success.