B'helro Mur'tar

Tentacle Swarm. When entering combat for the first time B'helro Mur'tar summons two Tentacles.

Tentacle
Armour Class: 16
Hit Points: 74(8d10+34)
Speed: 10 ft.
Actions:
Tentacle. Melee Weapon Attack: +16 to hit, reach 30 ft., one target. Hit: 20 (3d6 + 10) bludgeoning damage, and the target is grappled(escape DC 18). Until this grapple ends, the target is restrained. B'helro Mur'tar can have up to six tentacles, each of which can grapple one target

Innate Spellcasting. B'helro Mur'tar's spellcasting ability is Wisdom (spell save DC 19). B'helro Mur'tar can innatly cast the following spells, requiring no material component:
Cantrips (at will): alter self(can reduce his size to Medium), detect magic,control weather, poison spray, ray of frost, sending,  shocking grasp
3/day each: cone of cold, dispel magic, fog cloud, modify memory
1/day each: chain lightning, plane shift, wall of ice

Legendary Resitance (3/Day). If B'helro Mur'tar fails a saving throw, he can choose to save instead.

Magic Resitance. B'helro Mur'tar has saving throws against spells and other magical effects.

Magic Weapons. B'helro Mur'tar's attacks are magical.

Multiattack. B'helro Mur'tar can make two claw attacks.

Bite. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 24 (3d10 + 9) piercing damage plus 6 (2d6) cold damage.

Claw. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 15 (2d8 + 9) slashing damage.

Summon Tentacle. B'helro Mur'tar summons a tentacle ,up to maximum of six.

Lightning Storm. B'helro Mur'tar magically creates three bolts of lightning, each of which can strike a target B'helro Mur'tar can see within 120 feet of it. A target must make a DC 21 Dexterity saving throw, taking 22 (4d10) lightning damage on a failed save, or half as much damage on a successful one.

Fling. One Large or smaller object held or creature grappled by B'helro Mur'tar is thrown up to 60 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 18 Dexterity saving throw or take the same damage and be knocked prone.

B'helro Mur'tar can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. B'helro Mur'tar regains the legendary actions at the start of his turn.

Lightning Storm (Costs 2 Actions). B'helro Mur'tar uses Lightning Storm.

Fling. B'helro Mur'tar uses its Fling.