Boruna, The Corrupted Drider Queen

Legendary Resistance (5/Day): If Boruna fails a saving throw, she can choose to succeed instead.

Magic Resistance: Boruna has advantage on saving throws against spells and other magical effects.

Aura of Corruption (Recharge 6): A 60-foot-radius aura of swirling shadow emanates from Boruna. All enemies in this area must make a DC 24 Constitution saving throw or take 55 (10d10) necrotic damage and have their hit point maximum reduced by an amount equal to the necrotic damage taken. The reduction lasts until the creature finishes a long rest. If a creature’s hit point maximum is reduced to 0, it dies.

Spider Queen's Command: Boruna can summon 2d4 Shadow Infused Dryders, Crystalized Wretches, or Void-touched Beasts (see lesser enemies above) as a bonus action. These minions act on their own initiative but obey Boruna's telepathic commands. She can have up to 8 minions under her control at one time.

Web of Souls: Boruna's webbing is infused with the souls of the dead. Creatures who are restrained by her webs (from her Web ability) take 22 (4d10) psychic damage at the start of their turn. If a creature dies while restrained by her webs, Boruna regains 30 hit points.

Multiattack: Boruna can make three attacks with her Scimitar of the Abyss or two attacks and use one of her magical abilities.

Scimitar of the Abyss:

Melee Weapon Attack: +16 to hit, reach 15 ft., one target.

Hit: 32 (4d10 + 8) slashing damage plus 18 (4d8) necrotic damage. The target must succeed on a DC 24 Strength saving throw or be knocked prone.

Venomous Bite:

Melee Weapon Attack: +16 to hit, reach 5 ft., one target.

Hit: 28 (4d8 + 8) piercing damage plus 36 (8d8) poison damage. The target must succeed on a DC 24 Constitution saving throw or be poisoned for 1 minute. A poisoned creature is paralyzed while poisoned this way. The creature can repeat the saving throw at the end of each of its turns, ending the effect on a success.

Web (Recharge 5-6):

Boruna shoots webs in a 60-foot cone. Each creature in the area must make a DC 24 Dexterity saving throw or be restrained by the webbing. Restrained creatures can make a DC 24 Strength check as an action, freeing themselves on a success. The webbing can be attacked and destroyed (AC 15; HP 50; vulnerability to fire; immunity to bludgeoning, poison, and psychic damage).

Shadow Rift (Recharge 5-6):

Boruna opens a rift to the Shadowfell in a 30-foot-radius area within 120 feet of her. Each creature in that area must make a DC 24 Dexterity saving throw or be sucked into the Shadow Rift. On a failed save, a creature is banished to a nightmarish plane for 1 minute, taking 45 (10d8) necrotic damage at the start of each of its turns. A banished creature can make a DC 24 Wisdom saving throw at the end of each of its turns, returning on a success.

Command Minions:

Boruna can issue telepathic commands to her summoned minions. As a bonus action, she can choose one of her minions within 120 feet. That minion can use its reaction to immediately move up to half its speed and make one attack.

Shadow Step (Recharge 4-6):

Boruna can teleport up to 60 feet to an unoccupied space she can see that is in dim light or darkness. After teleporting, she has advantage on attack rolls until the start of her next turn.

Dark Benediction (Recharge 5-6):

Boruna empowers a summoned minion within 60 feet, granting it an additional 50 temporary hit points and allowing it to make one additional attack on its next turn. If this minion dies, Boruna regains 25 hit points.

Corruptive Web:

As a bonus action, Boruna can coat her weapons with a venomous web. Until the start of her next turn, her melee weapon attacks deal an additional 18 (4d8) poison damage, and creatures hit must succeed on a DC 24 Constitution saving throw or be poisoned for 1 minute.

Evasive Retreat:

When Boruna takes damage, she can use her reaction to move up to half her speed without provoking opportunity attacks.

Shadow Shield (3/Day):

When Boruna is hit by an attack, she can summon a protective barrier of shadow. She gains resistance to the triggering attack's damage, and the attacker must succeed on a DC 24 Constitution saving throw or be blinded until the end of its next turn.

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

Attack: Boruna makes one Scimitar of the Abyss attack.

Summon Minion (Costs 2 Actions): Boruna summons one Shadow Infused Dryder or Crystalized Wretch in an unoccupied space within 30 feet of her.

Web Blast (Costs 2 Actions): Boruna shoots webs at a target within 120 feet. The target must succeed on a DC 24 Dexterity saving throw or be restrained by webbing.

Regenerate (Costs 3 Actions): Boruna regains 50 hit points.