Legendary Resistance (4/Day, or 5/Day in Lair). If the dracolich fails a saving throw, it can choose to succeed instead.

Life Suppression. Creatures within 60 feet of the dracolich can’t regain Hit Points or be brought back to life.

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

Death Aura. 60' feet. The Ancient Alasklerbanbastos is imbued with an unholy aura of death. Any creature who starts their turn within 80 feet of him loses half their level in hit points. This loss of life can not be prevented, redirected, absorbed by any means.

Multiattack. The dracolich makes one Bite Attack and 2 Rend attacks or 3 Rend attacks. It can replace one attack with a use of Spellcasting to cast Ray of Sickness (level 2 version). If his breath weapon is ready it is a free action but he may only use it once per turn.

Bite. Melee Attack Roll: +19, reach 15 ft. Hit: 36 (4d12 + 10) Piercing damage, and the target has the Grappled condition (escape DC 20). Until the grapple ends, the target has the Restrained condition.

Rend. Melee Attack Roll: +16, reach 20 ft. Hit: 28 (3d12 + 9) Slashing damage plus 12 (2d6) Necrotic damage.

Necrotic Breath (Recharge 4–6). Constitution Saving Throw: DC 23, each creature in a 90-foot Cone. Failure: 78(12d12) Necrotic damage. Success: Half damage.

Lightning Breath (Recharge 4–6). Dexterity Saving Throw: DC 23, each creature in a 120-foot-long, 10-foot-wide Line. Failure: 88 (16d10) Lightning damage. Success: Half damage.

Spellcasting. The dracolich casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 22, +11 to hit with spell attacks):

At Will: Detect Magic, Invisibility, Mage Hand, Ray of Sickness (level 2 version)
1/Day Each: Create Undead (level 8 version), Finger of Death

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

Cast Spell. The Dracolich casts a spell from its spell options. The Dracolich can’t take this action again until the start of its next turn.

Cloaked Flight. The Dracolich  uses Spellcasting to cast Invisibility on itself, and it can fly up to half its Fly Speed. The Dracolich can’t take this action again until the start of its next turn.

Pounce. The dracolich moves up to half its Speed, and it makes one Rend attack.

Sickening Ray. The dracolich uses Spellcasting to cast Ray of Sickness (level 2 version). The dracolich can’t take this action again until the start of its next turn.

Sonic Boom. The Dracolich uses Spellcasting to cast Shatter (level 9 version). The Dracolich can’t take this action again until the start of its next turn.

Tail Slap. Melee Attack Roll: +19, 30 foot line. Hit: 23 (3d8 + 10) Bludgeoning damage. If the target is a Huge or smaller creature, it has the Prone condition. The Dracolich can’t take this action again until the start of its next turn.

Terrifying Presence. Wisdom Saving Throw: DC 19, each creature in a 30-foot Emanation originating from the dracolich. Failure: 11 (2d10) Psychic damage, and the target has the Frightened condition until the end of its next turn. Failure or Success: The dracolich can’t take this action again until the start of its next turn.