Guardian Naga

If it dies, the naga returns to life in 1d6 days and regains all its hit points. Only a wish spell can prevent this trait from functioning.

The naga is an 11th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 16, +8 to hit with spell attacks), and it needs only verbal components to cast its spells. It has the following cleric spells prepared:
Cantrips (at will): mending, sacred flame, thaumaturgy
1st level (4 slots): command, cure wounds, shield of faith
2nd level (3 slots): calm emotions, hold person
3rd level (3 slots): bestow curse, clairvoyance
4th level (3 slots): banishment, freedom of movement
5th level (2 slots): flame strike, geas
6th level (1 slot): true seeing

and the target must make a DC 15 Constitution saving throw, taking 45 (10d8) poison damage on a failed save, or half as much damage on a successful one.

The target must make a DC 15 Constitution saving throw, taking 45 (10d8) poison damage on a failed save, or half as much damage on a successful one.