Valería Commonbrook, Aspect of Levistus

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

Life Link. Valería takes half damage from all sources of damage. Whenever Valería takes damage, Levistus' true form takes the same amount. Whenever Valería is healed, Levistus' true form is healed for the same amount. 

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

Spellcasting. Valería is an 20th-level spellcaster. Her spellcasting ability is Charisma (spell save DC 20, +12 to hit with spell attacks). Valería can cast disguise self, charm person and invisibility at will and has the following spells prepared:

Cantrips (at will): eldritch blast, shocking grasp, mage hand, vicious mockery, chill touch

1st level (4 slots): silvery barbs, guiding bolt, cure wounds, bane

2nd level (3 slots): tasha's mind whip, mirror image, misty step

3rd level (3 slots): counterspell, dispel magic, thunder step, vampiric touch

4th level (3 slots): black tentacles, ice storm, summon aberration

5th level (3 slots): synaptic static, destructive wave, antilife shell

6th level (2 slots): heal, gravity fissure

7th level (2 slot): crown of stars, regenerate

8th level (1 slot): maddening darkness

9th level (1 slot): time stop

Dagger. Melee or Ranged Weapon Attack: +11 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 6 (1d4 + 5) piercing damage and the target must succeed on a DC16 Constitution saving throw or be poisoned. The poison lasts until removed by lesser restoration or similar magic. While poisoned this way, the target must make a DC16 Wisdom saving throw on each of its turns or begins to howl with rage and act that turn as if under the effect of the confusion.

War Caster.  When a hostile creature's movement provokes an opportunity attack from Valería, she can use her reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.

Valería can take 3 legendary actions per round. Valería regains spent legendary actions at the start of her turn. 

Cast a Spell. Valería casts a spell.

Void Tear. Valería rips open a lingering tear in the fabric of reality in a 10-foot radius centered on a point she can see within 120 feet. Any creature who enters this tear is transported to the inverse plane to face Levistus' true form. They must also make a DC 14 Sanity check or take 3d6 psychic damage.