Multiattack. The naga makes two Bite attacks. It can replace any attack with a use of Serpentine Gaze.
Bite. Melee Attack Roll: +5, reach 10 ft. Hit: 10 (2d6 + 3) Piercing damage plus 7 (2d6) Necrotic damage.
Serpentine Gaze. Wisdom Saving Throw: DC 13, one creature the naga can see within 60 feet. Failure: 13 (3d6 + 3) Psychic damage, and the target has the Charmed condition until the start of the naga's next turn.
Spellcasting. The naga casts one of the following spells, requiring no Material components and using Intelligence as the spellcasting ability (spell save DC 13):
At will: Mage Hand, Thaumaturgy