Fiendish Blessing. The AC of Isolde includes her Charisma bonus.

Magic Resistance Aura. While holding Nepenthe, Isolde creates an aura in a 10-foot radius around her. While this aura is active, Isolde and all creatures friendly to her in the aura have advantage on saving throws against spells and other magical effects.

Innate Spellcasting. Isolde's spellcasting ability is Charisma (spell save DC 14). Isolde can innately cast the following spells, requiring no material components:

1/day: plane shift (self only)

3/day each: alter self, command, detect magic

Multiattack. Isolde makes two melee attacks or uses its Fire Ray twice.

Nepenthe. Melee Weapon Attack: +10 to hit, reach 5 ft.., one target. Hit:11 (1d8 + 7) slashing damage, or 12 (1d10 + 7) slashing damage if used with two hands to make a melee attack. If the target is a fiend or an undead, it takes an extra 11 (2d10) radiant damage.

Fire Ray. Ranged Spell Attack: +7 to hit, range 120 ft., one target. Hit:10 (3d6) fire damage.

Fiendish Charm. One humanoid Isolde can see within 30 feet of it must succeed on a DC 14 Wisdom saving throw or be magically charmed for 1 day. The charmed target obeys Isolde's spoken commands. If the target suffers any harm from Isolde or another creature or receives a suicidal command from Isolde, the target can repeat the saving throw, ending the effect on itself on a success. If a target's saving throw is successful, or if the effect ends for it, the creature is immune to Isolde's Fiendish Charm for the next 24 hours.