Ursala the sea witch

Amphibious. Ursula can breathe air and water.
Innate Spellcasting. Ursula's innate spellcasting ability is Charisma (spell save DC 20, +12 to hit with spell attacks). She can innately cast the following spells, requiring no material components:
At will: detect thoughts, minor illusion, thaumaturgy                                                             3/day each: charm person, counterspell, darkness, dispel magic                                             1/day each: dominate monster, feeblemind, teleport
Deal Maker. Ursula can offer a magical contract to a willing creature within 30 feet. The creature must succeed on a DC 20 Charisma saving throw or be bound by the contract. While bound, the creature is charmed by Ursula and must obey her commands. The charm lasts until the contract is fulfilled or broken, or until Ursula dismisses i action

Multiattack. Ursula makes two tentacle attacks
Tentacle. Melee Weapon Attack: +9 to hit, reach 15 ft. one target. Hit: 17 (3d8 +4) bludgeoning damage, and the target is grappled escape DC 17). Ursula has four tentacles, ter ed each of which can grapple only one target.
Lightning Strike (Recharge 5-6). Ursula summons a bolt of lightning that strikes a point she is within 120 feet. Each creature within 10 feet of that point must make a DC 20 Dexterity saving throw, taking 44 (8410) lightning damage on a failed save, or half as much damage on a successful one.

Hex. Ursula curses a creature she can see within 60 feet. The target must succeed on a DC 20 Wisdom saving throw or have disadvantage on ability checks and saving throws of a type Ursula chooses Strength. (Dexterity, or Constitution) for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on a success.

Retributive Tentacle. When Ursula is hit by a melee attack, she can make a tentacle attack against the attacker.

Ursula can take 3 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.      Ursula regains spent legendary actions at the start of her turn.

Tentacle Attack. Ursula makes one tentacle attack.
Hex   Ursula uses her Hex bonus action at an upcast targeting an additional player
Lightning Surge:  Ursula uses her Lightning Strike action if available.