Apocryphal Lich Magus

Arcane Dismantlement. Whenever the lich successfully dispels or counters a spell with dispel magic, counterspell, or a similar spell, it can make an Intelligence (Arcana) check against a DC equal to the spell's level + the spell save DC of the spell's caster. On a success, the lich recovers an expended spell slot equal to, or less than, the dispelled spell's level.

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

Rejuvenation. If it has a phylactery, a destroyed lich gains a new body in 1d10 days, regaining all its hit points and becoming active again. The new body appears within 5 feet of the phylactery.

Spellcasting. The lich is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). The lich has the following wizard spells prepared:

Cantrips (at will): acid splash, mage hand, prestidigitation

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

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

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

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

5th level (3 slots): cone of cold, scrying

6th level (1 slot): disintegrate, globe of invulnerability

7th level (1 slot): finger of death, plane shift

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

9th level (1 slot): power word kill

Turn Resistance. The lich has advantage on saving throws against any effect that turns undead.

Paralyzing Touch. Melee Spell Attack: +12 to hit, reach 5 ft., one creature. Hit: 10 (3d6) cold damage. The target must succeed on a DC 19 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.

The lich 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. The lich regains spent legendary actions at the start of its turn. 

Cantrip. The lich casts a cantrip 

Paralyzing Touch (Costs 2 Actions). The lich uses its Paralyzing Touch. 

Sense Weakness (Costs 2 Actions). The lich telepathically probes a creature it can see, within the range of its telepathy, for its strengths and weaknesses. The target must succeed on a DC 19 Charisma saving throw, or the lich learns of the target's damage vulnerabilities, resistances, and immunities, as well as condition immunities and the exact number of hit points remaining. 

Frightening Apocrypha (Costs 3 Actions). The lich telepathically focuses a stream of forbidden knowledge on one creature it can see within 20 feet of it. The target must succeed on a DC 19 Wisdom saving throw, or become frightened for 1 minute. While frightened, the creature has disadvantage on Intelligence, Wisdom, and Charisma saving throws against the lich's wizard spells. The frightened creature 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 has advantage on Intelligence, Wisdom, and Charisma saving throws against the lich's wizard spells until the next time it fails to save against one of them, and is immune to the lich's gaze for the next 24 hours.