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

Limited Magic Immunity. Unless she wishes to be affected,Yun'Taal is immune to spells of 6th level or lower and all spells of the Necromancy School. She has advantage on saving throws against all other spells and magical effects.

Magic Weapons. Yun'Taal’s weapon attacks are magical.

Ancient Being. Yun'Taal can take three reactions per round, rather than only one per round. She also has advantage on saving throws against being knocked unconscious. If she fails a saving throw against an effect that would stun a creature, one of her unspent legendary actions is spent.

Regeneration. Yun'Taal regains 30 hit points at the start of her turn.

Learned Spellcaster. Yun'Taal has an amount of spell slots equal to a level 20 wizard except she has two level 8 and 9 spell slots instead of one.

Multiattack. Yun'Taal can use her Frightful Presence. She then makes three attacks: two with her claws and one with her tail. Any attack can be replaced with a Necromancy cantrip or all three with a Necromancy Spell. 

Claw. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 24 (4d6 + 10) slashing damage.

Tail. Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: 28 (4d8 + 10) piercing damage.

Frightful Presence. Each creature of Yun'Taal’s choice that is within 240 feet of Yun'Taal and aware of her must succeed on a DC 28 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to Yun'Taal's Frightful Presence for the next 24 hours.

Yun'Taal can take 5 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. Yun'Taal regains spent legendary actions at the start of her turn.

Bite. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 32 (4d10 + 10) slashing damage plus 14 (4d6) lightning damage or cold damage.

Blue Dragon Ancestry: Lightning Breath (Costs 3 Actions). Yun'Taal breathes lightning in a 120-foot line that is 10 feet wide. Each creature in that line must make a DC 28 Dexterity saving throw, taking 88 (16d10) lightning damage on a failed save, or half as much damage on a successful one.

White Dragon Ancestry: Cold Breath (Costs 3 Actions). Yun'Taal breathes an icy blast in a 90-foot cone. Each creature in that area must make a DC 28 Dexterity saving throw, taking 72 (16d8) cold damage on a failed save, or half as much damage on a successful one.

Innate Spellcaster (Costs 1 Action). Yun'Taal can Cast one Cantrip from the Necromancy school of magic with a DC of 28 or a +20 to hit.

Master Spellcaster (Costs 3 Actions). Yun'Taal can Cast one Spell of any level from the Necromancy school of magic with a DC of 28 or a +20 to hit.