Baernoloth

Innate Spellcasting. The baernoloth's innate spellcasting ability is Charisma (spell save DC 18). It can innately cast the following spells, without providing material components:

At will: alter self, clairvoyance, cure wounds, darkness, detect magic, detect thoughts, dispel magic, invisibility (self only), suggestion
3/day each: cloudkill, dimension door, fear, synaptic static
1/day each: power word pain, symbol, weird

Magic Resistance. The baernoloth has advantage on saving throws against spells and other magical effects.

Magic Weapons. The baernoloth's weapon attacks are magical.

Pain Echo (1/Turn). As a bonus action, the baernoloth targets one creature within 60 feet. The target takes psychic damage equal to the amount of damage it took from the baernoloth's last melee attack that hit it within the past 24 hours and must make a DC 18 Wisdom saving throw or be frightened until the end of the baernoloth's next turn.

Multiattack. The baernoloth makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) piercing damage plus 9 (2d8) necrotic damage. If the target is a creature, it must succeed on a DC 18 Constitution saving throw or have its hit point maximum reduced by an amount equal to the damage taken. The target dies if this attack reduces its hit point maximum to 0. The reduction lasts until removed by the greater restoration spell or other magic.

Claws. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

Teleport. The baernoloth magically teleports, along with any equipment it is wearing or carrying, up to 60 feet to an unoccupied space it can see.

Mass Pain Echo (Recharge 5–6). Each creature within 60 feet of the baernoloth takes psychic damage equal to the amount of damage it took from the baernoloth’s last melee attack that hit it within the past 24 hours and must make a DC 18 Wisdom saving throw or be frightened until the end of the baernoloth’s next turn.

The baernoloth can take three legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The baernoloth regains spent legendary actions at the start of its turn.

Claw. The baernoloth makes a claw attack.
Bite (Costs 2 Actions). The baernoloth makes a bite attack.
Teleport (Costs 2 Actions). The baernoloth magically teleports, along with any equipment it is wearing or carrying, up to 60 feet to an unoccupied space it can see.
Cast a Spell (Costs 3 Actions). The baernoloth casts a spell from its list of innate spells, using a spell slot as normal.