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

Spellcasting. Zadyrmortxes is an 20th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 23, +15 to hit with spell attacks). Zadyrmortxes has the following wizard spells prepared:

Cantrips (at will): chill touch, prestidigitation, ray of frost, toll the dead

1st level (4 slots): detect magic, magic missile, shield, thunderwave

2nd level (3 slots): acid arrow, detect thoughts, invisibility, mirror image

3rd level (3 slots): animate dead, counterspell, dispel magic, fireball

4th level (3 slots): blight, dimension door

5th level (3 slots): cloudkill, scrying

6th level (2 slot): disintegrate, circle of death, chain lightning

7th level (2 slot): finger of death, plane shift,mordenkainen’s Sword

8th level (1 slot): dominate monster, power word stun

9th level (1 slot): power word kill

Turn Immunity. Zadyrmortxes has immunity against any effect that turns undead.

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

Magic Weapons. Zadrymortxes' weapons are magical 

Multiattack. Zadyrmortxes can make two melee weapon attacks.

Longsword. Melee Weapon Attack: +11{"diceNotation":"1d20+11","rollType":"to hit","rollAction":"Longsword"} to hit, reach 5 ft., one target. Hit: 9 (1d8+5) slashing damage, or 10(1d10+5) slashing damage if used with two hands.

Shortsword. Melee Weapon Attack: +11{"diceNotation":"1d20+11","rollType":"to hit","rollAction":"Shortsword"} to hit, reach 5 ft., one target. Hit: 8 (1d6+5) piercing damage.

Handaxe. Melee Weapon Attack: +11{"diceNotation":"1d20+11","rollType":"to hit","rollAction":"Handaxe"} to hit, reach 5 ft., one target. Hit: 8(1d6+5) slashing damage.

Paralyzing Touch. Melee Spell Attack: +15 to hit, reach 5 ft., one creature. Hit: 10 (3d6) cold damage. The target must succeed on a DC 23 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Chill Touch (Cantrip). Ranged Spell Attack: +15 to hit, range 120 ft., one creature. Hit:18 (4d8) necrotic damage, and the target can’t regain hit points until the start of Zadyrmortxes' next turn. If the target is undead, it also has disadvantage on attack rolls against Zadyrmortxes until the end of its next turn.

Possession (Recharge 6). One humanoid that the ghost can see within 5 feet of it must succeed on a DC 15 Charisma saving throw or be possessed by Zadyrmortxes; Zadyrmortxes then disappears, and the target is incapacitated and loses control of its body. Zadyrmortxes now controls the body but doesn't deprive the target of awareness. Zadyrmortxes can't be targeted by any attack, spell, or other effect, and it retains its alignment, Intelligence, Wisdom, Charisma, and immunity to being charmed and frightened. It otherwise uses the possessed target's statistics, but doesn't gain access to the target's knowledge, class features, or proficiencies.

The possession lasts until the body drops to 0 hit points, Zadyrmortxes ends it as a bonus action, or Zadyrmortxes is forced out by an effect like the dispel evil and good spell. When the possession ends, Zadyrmortxes reappears in an unoccupied space within 5 feet of the body. The target is immune to Zadyrmortxes' Possession for 24 hours after succeeding on the saving throw or after the possession ends.

Two-Weapon Fighting. When Zadyrmortxes takes the Attack action and attacks with a light melee weapon that it is holding in one hand, Zadyrmortxes can use a bonus action to attack with a different light melee weapon that it is holding in another hand. Zadyrmortxes doesn't add its ability modifier to the damage of the bonus attack, unless that modifier is negative. If either weapon has the thrown property, Zadyrmortxes can throw the weapon, instead of making a melee attack with it.

Opportunity Attack. Zadyrmortxes can make an opportunity attack when a hostile creature that it can see moves out of its reach. To make the opportunity attack, Zadyrmortxes uses its reaction to make one melee attack against the provoking creature. The attack occurs right before the creature leaves its reach

Zadyrmortxes 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. Zadyrmortxes regains spent legendary actions at the start of its turn.

Cantrip. Zadyrmortxes casts a cantrip.

Multiattack (Costs 2 actions). Zadyrmortxes makes two melee attacks.

Paralyzing Touch (Costs 2 Actions). Zadyrmortxes uses its Paralyzing Touch.

Frightening Gaze (Costs 2 Actions). Zadyrmortxes fixes its gaze on one creature it can see within 10 feet of it. The target must succeed on a DC 18 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to the Zadrymortxes' gaze for the next 24 hours.

Disrupt Life (Costs 3 Actions). Each non-undead creature within 20 feet of the lich must make a DC 18 Constitution saving throw against this magic, taking 21 (6d6) necrotic damage on a failed save, or half as much damage on a successful one.

Possession (Costs 3 actions). Zadyrmortxes recharges and uses its possession