Arakna

Shapechanger. Arakna can use her action to polymorph into a Gargantuan spider, or into her humanoid form. Her statistics, other than her size, are the same in each form. Any equipment she is wearing or carrying isn't transformed. She reverts to her true form if she dies.

Innate Spellcasting. Arakna's innate spellcasting ability is Charisma (spell save DC 19). She can innately cast the following spells, requiring no material components:

At will: Silence, Web

3/day each: Banishment, Greater Invisibility

1/day each: Wall of Thorns, True Seeing

Spider Climb. Arakna can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Legendary Resistance (3/Day). If Arakna fails a saving throw, she can choose to succeed instead.

Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 19 (2d10 + 8) piercing damage, and the target must make a DC 22 Constitution saving throw, taking 18 (4d8) poison damage on a failed save, or half as much damage on a successful one.

Web (Recharge 5-6). Arakna can shoot webbing at a creature within 60 feet. The target must succeed on a DC 19 Dexterity saving throw or be restrained by webbing. As an action, the restrained target can make a DC 19 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 15; HP 30; vulnerability to fire damage; immunity to bludgeoning, poison, and psychic damage).

Spider Summoning. Arakna can magically summon 1d4 giant spiders. These creatures appear within 60 feet of her and act immediately on her turn. They remain for 1 hour, until they die, or until Arakna dismisses them as a bonus action.

Arakna 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. Arakna regains spent legendary actions at the start of her turn.

Attack. Arakna makes one attack with her claw.

Web. Arakna casts the Web spell.

Spider's Whisper (Costs 2 Actions). Arakna targets one creature she can see within 60 feet. The creature must succeed on a DC 19 Wisdom saving throw or be cursed. While cursed, the creature has disadvantage on ability checks, saving throws, and attack rolls made against Arakna.