Calthon

Necromancy. At the start of Calthon’s turn, it creates (2d8+2) zombies

Legendary Resistance (4/Day). If Calthon fails a saving throw, it can choose to succeed instead.

Unusual Nature. Calthon doesn’t need air, food, drink, or sleep.

Multiattack. Calthon uses either Wrath of Hades or Spellcasting. Calthon also uses Psychic Whisper twice.

Wrath of Hades. Calthon touches one creature and summons 8 souls to drag the target down to the underworld. The target must make a DC 19 Wisdom saving throw or take 34 (10d6+4) Necrotic damage on a failed save, or half as much on a succesful one.

Psychic Whisper. Calthon targets one creature it can see within 120 feet of itself. The target must succeed on a DC 17 Wisdom saving throw or take 25 (6d6 + 4) psychic damage and be stunned until the end of Calthon’s next turn as incomprehensible whispers fill the target’s mind.

Spellcasting. Calthon casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 17):

At will: chill touch, false life, inflict wounds

2/day each: vampiric touch, blight

Far Realm Step. Immediately after taking damage, Calthon, along with any equipment it is wearing or carrying, magically teleports up to 60 feet to an unoccupied space it can see.