The naga is a 5th-level spellcaster (spell save DC 12, +4 to hit with spell attacks) that needs only verbal components to cast its spells.
If the naga was a guardian naga in life, its spellcasting ability is Wisdom, and it has the following cleric spells prepared:   Cabtrips (at will): mending, sacred flame, thaumaturgy
1st level (4 slots): command, shield of faith
2nd level (3 slots): calm emotions, hold person
3rd level (2 slots): bestow curse   If the naga was a spirit naga in life, its spellcasting ability is intelligence, and it has the following wizard spells prepared:   Cantrips (at will): mage hand, minor illusion, ray of frost 1st level (4 slots): charm person, sleep 2nd level (3 slots): detect thoughts, hold person 3rd level (2 slots): lightning bolt