Legendary Resistance (3/Day, or 4/Day in Lair). If Vioghyl fails a saving throw, he can choose to succeed instead.

Life Suppression. Creatures within 60 feet of Vioghyl can’t regain Hit Points.

Magic Resistance. Vioghyl has Advantage on saving throws against spells and other magical effects.

Soul Gem.The dracolich has a magical gem. If the dracolich is destroyed while the gem is on the same plane of existence as it, the dracolich gains a new body in 1d20 days days, regaining all its Hit Points and appearing within 5 feet of the gem.

The gem is a Tiny object that has AC 20; HP 50; and Immunity to Necrotic, Poison, and Psychic damage. The gem regains all its Hit Points at the end of every turn, but it turns to dust if reduced to 0 Hit Points. If the gem is destroyed, the dracolich can create a new one by completing an 8-hour ritual using a gem worth 1,000+ GP and by expending 5,000 GP, which the ritual consumes.

Multiattack. Vioghyl makes three Rend attacks. He can replace one attack with a use of Spellcasting to cast Blight, Ray of Sickness (level 6 version), or Shatter (level 3 version). Alternatively, he can replace two attacks with a use of Spellcasting to cast any other spell.

Rend. Melee Attack Roll: +14, reach 10 ft. Hit: 18 (2d10 + 7) Slashing damage plus 18 (4d8) Necrotic damage.

Necrotic Breath (Recharge 5–6). Constitution Saving Throw: DC 20, each creature in a 90-foot Cone. Failure: 52 (8d12) Necrotic damage. Success: Half damage.

Spellcasting. Vioghyl casts one of the following spells, requiring no Material components and using Intelligence as the spellcasting ability (spell save DC 21, +13 to hit with spell attacks):

At Will: Blight, Detect Magic, Dispel Magic, Invisibility, Mage Hand, Prestidigitation, Ray of Sickness (level 6 version), Shatter (level 3 version)
2/Day Each: Dimension Door, Scrying Sending, Speak with Dead
1/Day Each: Chain Lightning, Create Undead (level 8 version), Finger of Death, Power Word Kill

Protective Magic. Vioghyl casts Counterspell or Shield in response to the spell’s trigger, using the same spellcasting ability as Spellcasting.

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, Vioghyl can expend a use to take one of the following actions. Vioghyl regains all expended uses at the start of each of his turns.

Pounce. Vioghyl moves up to half his Speed, and he makes one Rend attack.

Sickening Ray. Vioghyl uses Spellcasting to cast Ray of Sickness (level 6 version).

Terrifying Presence. Wisdom Saving Throw: DC 21, each creature in a 20-foot Emanation originating from Vioghyl. Failure: 13 (2d12) Psychic damage, and the target has the Frightened condition until the end of its next turn. Failure or Success: Vioghyl can’t take this action again until the start of his next turn.